The detail in this answer is somewhat in disproportion to the detail in your question, since I want to help you to the best of my ability. It is, however, much easier for a solution-provider to give succinct, accurate, relevant and useful answers if the customers helps the process, as much as possible, by providing as much background information as possible.
You give no specific information about either the PC's or the TV's model number or specifications and are yet to respond to the other expert's valid prompt for additional details, so I will assume that you are only interested in general non-specific advice, as that is all that I will be able to offer you because of the sparse information in your question.
If both your computer and your TV have Video Graphics Array (VGA), Digital Video Interface (DVI) or High Definition Multimedia Interface (HDMI) ports, then you can connect the two devices with the appropriate VGA, DVI or HDMI cable.
If your TV does not have the above ports but only has Radio Corporation of America (inventor - RCA/Phono) connectors, then you can use the appropriate VGA to RCA/Phono, DVI to RCA/Phono or HDMI to RCA/Phono Adapter Cable between the TV and the PC (see images below).
Since all cable interconnections suffer from some degree or other of signal degradation os dissipation and gold is the most efficient conductor amongst the metals commonly used for cable connections, cables with gold plated connectors perform the best and therefore cost more than standard cables with connectors made with cheaper, less conductive metals. You should consider buying the best cabling that you can afford.
Once connected, if your TV has a Remote Control, press:
Menu -> Input (Signal/Device) Source -> PC -> Select/OK.
If you have no RC, then you can try using the Program or Channel selector buttons on the TV's control panel to manually select the Input Device.
When the Desktop PC is powered up, after setting up the TV as described above, the PC should send the image to the TV.
If the above information does not match the specifications of your equipment, them please post further background information here and one of the experts here will try to offer you further advice.
Gold Plated Male to VGA Cable
Gold Plated Male to Male HDMI Cable
Gold Plated Male to Male HDMI/VGA to RCA Adapter Cable
Gold Plated Male to Male DVI to RCA Adapter Cable
Gold Plated Male to Male DVI Cable
Standard Male to Male DVI Cable