You can add one more than one course to a Membership.
To add an additional course to a membership that you've already created that already includes a course. First login to the Member App software. Once you've logged in then navigate to the 'Memberships' page.
Find a membership you'd like to add a new course to:
Navigate to the bottom of the membership and click on the '+ Create New Course'.
You'll be redirected to the course setup up wizard.
Go through all required steps and set up your new course. For more details on how to create a new course see this article.
If you need to set up one more course, you can do it. There's no limit to the number of courses you can create within one membership.