Forum Width - setting a pixel limit?

[Fulla]

How do I make my forum centered but cannot exceed 1000 pixels in width. Currently it takes up the whole screen!!

I was able to do it in 3.x.x, but how to in 4.x.x please?

[peugeot405]

in additional css add folowing code:

.body_wrapper {
    margin: 0 auto;
    padding: 10px 20px;
    width: 1000px;
}

[Fulla]

Almost works thanks

How do I get the top of the forums to also have a pixel limit?

Can see what I mean here:
http://www.sc2arcade.com/forums/

Top/Header is still very wide.