I can provide a step-by-step guide for your specific software version!
For modders running or HEN (Homebrew Enabler) , installing the PS2 Classics Placeholder RAP file via reactPSN or webMAN MOD is the standard first step. It allows them to convert any ISO of a PS2 game into a PKG and run it as if it were an official Sony Classic. Ps2 Classics Placeholder Rap File
For a homebrew user wanting to play their own PS2 ISOs on a PS3, this was a nightmare. You couldn't just "copy and paste" a game. The system expected a paid license to decrypt the data. Without that license, the game was gibberish to the console. I can provide a step-by-step guide for your