I have just bought a new 3 in 1, and wish to

You can have as many printers as you want installed on a single pc. Some printers use a parallel port which uses a 25 pin on the back of your pc and others use USB which most computers have 2-4 of. If it's a usb connection just plug it in and your computer should detect it and ask you if you want to install it. When you go to print you'll have the option of using either printer.