Instructor are basically case workers but they are called instructors under attendance function.
Instructors can only be assigned from the case template when the attendance check is on, as shown in [Copy Link].
Go to How to create Case Template and follow the steps once you create all the programs and activities Click on any activity you want to assign the worker to.
Activities edit page will open. Click on case worker, it will list down all the workers created in the system. Select the worker and Topics need to be included for the particular subject and click on save to update the activity.
Add all the workers required on the case template and click on save to update the case template.