It sounds like they are describing two ways of studying for a test.
Method A = something that is probably described in a previous sentence.
Method B = practice testing.
Your sentence means the following:
If you use Method A, you will run out of time and you likelywon't remember the information.
But, if you use Method B (practice testing), you will do better.
"As well as" is a way to compare things.
Using Method A, you won't do "as well as" if you use Method B.
You could also say:
You will do better if you use Method B than you will if you use Method A.