Fortunately for you, "VGA" is "RGB". All you need is a cable that will let you hook the two together and some software that will get your PC to output video at the appropriate scanrates.
The former I can't help you with because you haven't posted any further information. Do you have BNCs for RGB inputs on your TV? SCART? Something else?
The latter is generally solved for most people by either an ArcadeVGA or Soft15kHz or a similar tool or driver hackery. If you're not running Windows, then the answer is different.