(trusting my "remembery" not to have been too severely dimmed by VV30) - you right click on the clip you want to slow down, left click on insert velocity envelope, you'll see a line (mine is blue) across the length of the clip, left click and drag that line downward to slow the motion of that clip. If you need to maintain all the action in that clip, you'll need to resize it. As far as I can recall, that's all there is to it.

Caruso