ps2 matrix moded-how to use it?

so I got a ps2 fat for a dirt cheap, but the thing is I have never seen moded ps2 and dont know how to load games to usb.

ps boots up and displays Matrix logo, then it shows 4 exclamation marks.

can anybody tell me where to start and what should I do to get games on usb flash drive?

I was google-ing and found something like "you should install OPL" then defragment drive...so I totally confused