We recommend leaving GS Plugin as-is if you’re not experiencing visual artifacts or glitches.
You can find this under Config, Plugins/BIOS selector. It’s time to configure PCSX2 Graphics Settings. Make sure to put a Check on Use Default Setting, then click on Finish and proceed to the next setting.
Locate the PS2 BIOS file you have downloaded and select it. Leave everything as-is and proceed to PCSX2 Bios. If everything is installed correctly, you should be seeing the PCSX2 First Time Configuration Window.
This video tutorial can help you tweak the most advanced settings that we won’t be covering for this guide.