Obtaining PS2 games can be as easy as buying PS2 DVDs off eBay. However, an original game DVD is not enough to make PCSX2 work. You'll also need the BIOS dumped from your PS2. The PS2 BIOS is copyrighted by Sony so getting it from anywhere but your own PS2 is illegal. You will have to own an actual PS2 console to dump the BIOS from before you can start playing PS2 games on the emulator. There is no region locking so if you have a PAL BIOS on your PS2 you can still play NTSC games, and vice versa.