Since the PS2 doesn't have a "Mod Loader" like the PC version, you must patch the game's internal data files and rebuild the ISO. To modify an ISO, you will typically need:
Change CJ’s appearance or swap his model with other NPCs. How to Install a Mod Menu on a PS2 ISO gta san andreas mod menu ps2 iso
Most mod menus replace the main.scm and script.img files. Since the PS2 doesn't have a "Mod Loader"
Tools to extract and replace files within the ISO. gta san andreas mod menu ps2 iso
To edit textures if your mod menu includes custom icons. 2. The Installation Process