Legal and practical considerations:

PCSX2 requires a PlayStation 2 BIOS file to boot games. This is the system software of the original console.

to "stream" their screen to friends, allowing for online multiplayer by simulating local couch co-op. Where to Find the Game Internet Archive

Because WWF SmackDown! Just Bring It is a vintage console game, you cannot simply open a web browser and click a "play now" button. Instead, you use a PC emulator to mimic the PlayStation 2 hardware, combined with peer-to-peer network features to connect with other players. The primary tools you need are:

If you want to stay strictly within legal bounds, you must buy a physical copy of the game on eBay or at a retro game store and rip the ISO file yourself.