If you haven't done that yet, the first thing you need to do is start adding questions to your exam. Quite obvious, right? =)
You can do that by going to EXAMS (in your dashboard) > create new exam > start adding questions.
At this point, you can add more questions to your exam than you'll actually need/want at the end (because you can have the system randomize all the questions or only a selection of them).
You can find the setting to randomize your questions under "Behavior". It's right at the bottom of that page, where it says "Question order":
If you choose "Random", the questions will be shuffled, and you can even choose to only use a selection of the total amount of questions. (Maximum number of questions that are to be picked).
To have access to this setting, you need to have a Business Owl account - at the minimum.