How am I meant to get PS2 game cheats?
One that I really like and isn't mentioned in that post is gamefaqs.com. The site is nicely structured and includes all sorts of information about games on nearly all platforms. You'll find cheats, walkthroughs, tips, tricks, glitches, game information, etc. there.
you could search Google. Or you could check out the sites recommended in this MakeUseOf article: Top 10 Websites For PlayStation 2 Free Game Cheats.
+1 for MakeUseOf article :-)