Hi @lauren.kennedy,
This is a great question!
Reading through the code isn’t fun… But it always helps. I think in particular Chapters 3, 5, 6, 7, & 10 come up a lot on the exam, so I would focus on reviewing those chapters! More important than memorizing everything in the code (which is probably impossible I think) is understanding how the code is organized, where to look in the code for the answers you need, and what the code is concerned with or the methodology behind it.
If you can get your hands on a copy of the Code Commentary through work I would definitely see if you can borrow it for a couple days. It is a huge help in understanding some of the more ambiguous sections.
Ching’s “Building Code Illustrated” is also a great resource for helping learn the code:
https://www.wiley.com/en-us/Building+Codes+Illustrated%3A+A+Guide+to+Understanding+the+2018+International+Building+Code%2C+6th+Edition-p-9781119480358
Plus, it has pictures 
.
The International Code Council has some free training on the code at the link below:
https://www.iccsafe.org/products-and-services/i-codes/code-development/cs/introduction-to-building-codes/
Last but not least, try to find practice questions that force you to look through the code. Look for questions that ask you about occupancy classifications, allowable building areas/heights, construction types, occupancy counts, and fire/smoke protection requirements!
Check out some of the old practice quizzes on the Community below:
Hope this helps!
-Darion