Help! How do i make login box?

Ok, this is probably very simple answer to this. I wanted to know how you make the regular rectangle login box that i see on most vbb sites. Im helping a friend set his up, and cant figure it out. For example, just showing a login screen in the middle of the index page, instead of showing part of the board, with the tiny login thing in the lower right hand corner of the board.

Any help greatly appriciated.
Thanks