You define the text and fonts in the description.ext. Best way to see an example is to unPbo a mission where you've seen custom texts in the intro. Then (usually in the beginning of the description.ext) there will be long definitions of different fonts and what sizes they should be.
Next step is to explain to the game that it should use your custom title text and not the one that came with the game. This however, I don't know anythinbg about. Go have a look in the ed depot ;D
But I think it will be easier when you know what your looking for. Most of the huge, dashing, red/blue/yellow texts you see in intro's (that looks like logos) are actually pictures that is called using the command cutRsc.
Hope this will help you get started at least.