Passive scanning involves inspecting the traffic going through Burp. It does not send any additional requests to the target application.
If you're using Burp Pro, then you will already have 2 default scan tasks, one to add items to your site map and another to passively scan all traffic through Burp.
To discover vulnerabilities using tools like the Collaborator, you would need to perform an active scan instead (as this includes sending additional requests to the target application).
If you are planning on using Infiltrator at any point, please make sure that you have fully read our documentation first, as the use of Infiltrator will permanently modify an application's bytecode. You can find our documentation
here