The application package of any professional test should include an overview of the test, a list of reference materials, testing day requirements, and the content area for the groups of questions. Do you have all that?
With all that, study the reference materials. Read the intro (forward), the table of contents, definitions and the index. Look for unfamiliar terms. There are probably things you already know about but are worded differently. There is a lot of local slang in our industry. Do you really tell your helper to go get some notification appliances off the truck? Or do you say bring me three horn/ strobe combos?
Don't worry so much about remembering specifics; remember where to find information.
You'll never remember tables and calculations; you need to know which tables and which calculations to use when.
Find practice questions and do a dozen and stop. Check your work. You'll probably bomb every one of them and that's normal. The objective here is to learn how they phrase their questions, what language they speak, etc. Once you figure that out, do as many test questions as you can.