For porting or emulation? Because either way I'd say you're going to need to start learning a programming language or two, but for porting you're still going to need access to the source code so then you'd have to get a qualification, like a bachelor's degree, in computer science or something similar, then start working your way up in the game's industry by taking entry level jobs and building your portfolio, and then hopefully one day you'll end up working for the developer who made one of the games you want to port and you could say 'Hey, guys, can I have the source code for this game to make a Vita port?' and they'll probably say no, either because they don't have the source code anymore or because they don't want you working on a Vita port. But for emulation you could probably start by looking at PS2 emulators that are already out there and try porting one of those to the Vita - but again, the Vita isn't really powerful enough to emulate PS2 games so the best you'd get is a proof of concept running games at 1fps.