The Repo also has the PS2 bios files if you need them. When you're in the Repo, go to the "Extras" menu at the top and select "Bios Files". Once you have the bios files, you'll need to extra the 7z file with the program 7zip and put them in a folder path you can easily find.
Next, in the PCSX2 emulator, select "Bios" in the "Settings" menu at the top of the window. Click "Browse", in the new window that appeared go to the folder path where you put your bios files and the "Select Folder". This should populate the BIOS Selection menu. If they don't appear, click the "Refresh List" button.