To update a user's role (for example, from Subscriber to Student Staff), follow these steps:
Navigate to Engage > Subscribers (CRM)
Search for the user you wish to update
Hover over the user's name and select 'Edit'
Scroll to the 'Role' field and select the role permission you wish to assign this user from the drop-down list of options
Scroll all the way to the bottom and click the 'Update User' button. Voila!
If you need a refresher on the different permissions each user role type has, read this.