How to make mirror image of second monitor we cannot make the mirror image in our pc which is also connected with first monitor by rgb connector

Specify: what sort of computer are you using? PC? Mac? Android?
What OS version? Windows 7, 8, 10? Mac version?
What kind of output connectors are on your device? VGA, HDMI, lightning port, DVI, other?
What kind of input connectors are on your second monitor?
What are you trying to do with the second monitor? Simultaneously see a second app beside your other monitor (extend)? See the same exact image as the other monitor (duplicate)? Send the same/duplicate image (duplicate screen) to a projector, or send a different image to it (extend)?
If you can answer these questions, your inquiry will be easy to solve. Without that info? Hard to answer.

Computer Monitors

Nintendo home consoles are designed for use through home televisions and VCRs, using standard A/V, S-Video, component, or RF connectors (for older systems). Computer monitors typically do not have these connections. There are however two ways a hookup to a computer monitor could be accomplished:

With a PC TV Card:
A TV card inserted into your PC may allow you to connect your system if the card has the proper connections (such as RF, A/V, S-Video, component, or Coaxial). However, we have found that the image quality is not as clear as it is on a TV, in most cases.
With a Direct Connection (RGB or DVI Cables):
Nintendo does not manufacture any cables to make an RGB or DVI connection. While other companies may manufacture wires that can make this possible, we are not able to recommend them, as they are not licensed by Nintendo.

Computer Monitors

Nintendo home consoles are designed for use through home televisions and VCRs, using standard A/V, S-Video, component, or RF connectors (for older systems). Computer monitors typically do not have these connections. There are however two ways a hookup to a computer monitor could be accomplished:

With a PC TV Card:
A TV card inserted into your PC may allow you to connect your system if the card has the proper connections (such as RF, A/V, S-Video, component, or Coaxial). However, we have found that the image quality is not as clear as it is on a TV, in most cases.
With a Direct Connection (RGB or DVI Cables):
Nintendo does not manufacture any cables to make an RGB or DVI connection. While other companies may manufacture wires that can make this possible, we are not able to recommend them, as they are not licensed by Nintendo.

Sadly, RGB cannot carry sound. In order to hear the laptop sound on the television, You'll need to get an 1/8" headphone connector to RCA (White and Red plug) cable and connect it to the same input as the video is plugged in.

You'll need a VGA to Video composite / S-Video converter (commonly called PC to TV converter), this device will allow you to connect the VGA output to composite video input of your TV.

Computer Monitors

Nintendo home consoles are designed for use through home televisions and VCRs, using standard A/V, S-Video, component, or RF connectors (for older systems). Computer monitors typically do not have these connections. There are however two ways a hookup to a computer monitor could be accomplished:

With a PC TV Card:
A TV card inserted into your PC may allow you to connect your system if the card has the proper connections (such as RF, A/V, S-Video, component, or Coaxial). However, we have found that the image quality is not as clear as it is on a TV, in most cases.
With a Direct Connection (RGB or DVI Cables):
Nintendo does not manufacture any cables to make an RGB or DVI connection. While other companies may manufacture wires that can make this possible, we are not able to recommend them, as they are not licensed by Nintendo.

If the projector has two RGB inputs (they will be blue & look like female serial ports and be marked input1 & input2 or possibly RGB1 & RGB2) then both PC's can be connected, but only one image from one of the PC's can be displayed at a time. To change between them use the "input" button on the projector or remote control to switch between RGB1 & RGB2. If your projector has only one RGB connector at the back it is still possible to use the video input for the second PC but you will need a special adaptor for the RGB cable from one of your PC's.

You need to change the input signal, get into the menu on your monitor and change the signal from rgb to dvi, hdmi or vga dipending on what cable you using for connection.
There is NO rgb connector on that monitor

Good luck

Adobe RGB enables more vivid color reproduction, for Adobe RGB is capable of more color space than sRGB. It offers more flexibility than sRGB on image processing and image retouching. Please note, however, a normal PC monitor cannot realize the color reproduction effect, for the available color range of the monitor is restricted by its specification. Further, an image with Adobe RGB ICC profile may be reproduced in poor color depth unless color management is provided in advance. Meanwhile, there may be cases that the Adobe RGB effect is realized in printing out, as some colors can be reproduced by a printer.

It is possible to reproduce the more vivid color by Adobe RGB because this can obtain more color space than sRGB. At processing image and editing the degree of freedom of Adobe RGB is high. However some colors cannot be reproduced on monitor of PC, and sometimes the images look almost same as those recorded by sRGB. Some cases you can obtain the effects when printing as some colors can be reproduced by printer though the colors which are impossible to reproduce on monitor of PC.