Changing Roles
Users who have the Primary Owner or Owner roles in Milestone can modify the roles of other users. To change a user’s role, go to the Members page.

Select User Actions for the user you want to modify. Select their role from the menu:
Make Admin
Make Member
Make Mentor
For Primary Owners, the option to make a user an owner is also available.
After selecting the user’s new role, the user will be assigned to the role that was selected.