All the short video tutorials related to how to use the programs can be found here.
There are more than a few ways to go about editing clip lengths within the program so it may be easier and quicker to find a method you prefer from the tutorials than wait for several different replies on the forum.
See the tutorials here - in particular the movie Edit Pro Basic Editing parts 1 & 2 - though done in an older version of Movie Studio - previously called Movie Edit Pro the principles also apply to Movie Studio.