need help downgrading my psp ver 4.05

I dont know where to start cuz im new to all of this. If someone could help me it would be great.

edited: Don't ever make another thread in all caps lock. Its not cool.

make a pandoras using the guides in the tutorial section. If it is a slim use this link for the mms files http://www.youtube.com/watch?v=FMxvSVjK ... feature=iv . if it is a phat just follow the whole tutorial.