There are a lot of resources for that.
Start with the Qlik Sense Help
May be take some free online courses (or pay for all)
Watch the Qlik Sense videos
Purchase a ebook may be...
Good luck on your test
If you're going to take the Data Architect or the Business Analyst exams, I'd also recommend you to build several apps so you get familiar with the interface and bump with the most common issues in the platform. I took the Business Analyst test a couple of weeks ago and there are a lot of questions about the specific location and name of certain functions.