Open the ticket and click "No Location" in the upper left corner. Then select the correct location.
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The location can be updated at any time (i.e. if the location changes or if you want to copy the ticket to a new area).
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If you want to add a new location to the list, click on the "Locations" icon on the dashboard. Click "Add a New Location". Be sure to select a new color to go along with the new location. That location will immediately be available for everyone to use.