The on-line homework is a minimal assignment. If you do not understand how to work the problems from the section when you have finished the assigned problems, you should work additional problems, either from the book or on line.
You should work on your homework like you will take the test. This means that you should work problems out on paper, using a calculator that you will have available during the test. You should use your cheat-sheet to work on your homework. This will help you fine tune the cheat-shteet.