Once an exam (or even part of it), is created in Blackboard, you have to set the Test Options for that exam. If you are creating it in Blackboard, the system will send you to this page after creating your questions. If you created it another way (like Respondus Campus-Wide), simply click on the carrot next to the exam and click Edit the Test Options.
Once there, there are several settings to manage. Not all are important/necessary but here are the highlights.