You can add new instructors in a course if you are already in the course as an admin.
To add a new staff member, follow these steps:
Step 1: Within the Instructor tabs, click on Membership.
Step 2: Enter the instructor's email address in the box, then click Enroll.
Step 3: If your instructor does not already have a Credo account set up, they will receive an email and be asked to click on a link in that email to verify their account. Once they have done that (or if they already have a Credo account previously) scroll to the bottom of the page to add them as staff. If they need to be able to view as a specific student, change the dropdown to Admin. Enter their email, then click Add.