Hello.
First of all, is your TV on the VGA input? If yes, and the cable is connected, then are your video rivers correctly installed?
If the drivers are okay, then doing this might activate the VGA output. Go to Resolution Settings, or Screen Resolution, by right-clicking on the desktop. Next, click on the DETECT button. This will detect any connected monitor through VGA.
Next, adjust the resolution to a correct one. Most TV will only accept 1024x768, 1360x768 or 1920x1080 through the VGA. Anything else might result in a bad picture.