To edit who holds various Positions within your organization, navigate to your organization's Action Center. Use the Switchboard to enter the "Manage" view. If you are a member of the organization, you will see its name listed here and can select it to enter the organization's Action Center. If you are not a member of the organization but you have access to the organization through other means, you can also search for the organization within Manage, or open it from the organization list in the corresponding branch. 

Once you are in the Organization Action Center, open the pancake menu ( ≡ ) on the upper left and navigate to the Roster section.

If you first need to create a new Position, please note that you will need to hold the correct level of access to manage the Roster in order to make these changes.

On the Roster page, find the user for whom you would like to add, change, or remove a Position. Click the edit button under Positions to the far right of that user's name. A list of all available Positions will populate. Click the check box next to the position you would like to add or remove from that user, and then select Save. The user's permissions within the organization will be updated based on the Positions they hold.