The pre requisite to take the F5 402 exam is that you are currently a F5 CTS for LTM (301a and 301b) and DNS (302). These exams would have already exposed you to BIG-IP LTM and DNS. However, you should also read on and have an idea what are the other BIG-IP modules and their functionality.
The F5 402 exam blueprint already gives you the topics you will need to familiar with.
It really helps if you have hands on experience on working on cloud environments, such as AWS and Azure, and container environments such as in Kubernetes. For me, it was a bit of AWS and Kubernetes.
You will need to be familiar with cloud terminologies - services, features, etc - and how they relate to cloud vendors.
Familiarity with container orchestration terminologies such as in Kubernetes will also help.
Bundle these Cloud/Container terms and features and how they relate to BIG-IP deployments in the cloud, plus, mapping them per the F5 402 exam blueprint, will help you organize your knowledge and prepare for the exam.
Looking back and while preparing for the exam, here are the documentation which I would start to review and build a knowledge map. There are links in the articles that would supplement the concepts described, my suggestion, consult the F5 402 exam blueprint and see if you need more familiarity with a topic after reading thru the articles.