by specific module
I found that the easiest way was to select "custom study" and then select "gleim specific module(s)".
Some modules are very small depending on the test you are taking. Select one or two modules, keep it around 20 questions. Do it over and over until you get 100%. Then select some more modules. When you have the material all covered take some practice tests in the format that your testing center uses.
good luck (hint, during the test you will find that you won't even have to read the question, you will see the correct answer)