You assign a practitioner to a location by clicking on the 'locations' section in their record. This then brings up the locations they are assigned to (if any).
When the locations load, in order to add a new location to this practitioner, you must first click 'Edit'
Once you the click 'Edit', 'Add Location' will then appear, click this and it brings up the box below. You choose the location and set their first and followup charges.