down-grade my wordpress

I’m following a video tutorial in which the person seems to use version 3.0.4
He has an option I can’t find in mine so I need someone who can help me change my version 3.1 to version 3.0.4 to see if that works.
The problem is “I have installed a new plugin but can’t find its button at the left lower bottom of my plugins page.I don’t even have the super admin button he has on his screen.”
Please help me now…