NOTE: You need to be a Customer Admin to perform change member permissions do this

Navigate to Edit current Customer in the upper left corner, and then switch to the Members tab in the right area of the view. You will then see a list of all the members that currently are associated with your organization:

Choose to Edit a member by clicking on the pencil icon. The member's details will show up above the list with their information filled in.

Change the role by expanding the dropdown and selecting those roles that the member should have:

When you are satisfied with the selection, click Done:

Save the changes by clicking Save User:

Done! Note that the member that was changed will not see the changes until they open the application anew, or performing a Refresh in their browser.