In order to set an end date for a lease, the lease must be time limited. When you set an end date for a lease, a lease length will be automatically calculated.
To to set an end date for a lease:
Open a lease. For more information on how to do so, see section 4.6. or 6.1.
Go to the lease card (see image below).
Click the tab called "Dates" (see image below). Within the tab called "Dates" you will, among other things, find a field called "End date".
Set an end date for the lease you are working with by clicking the field "End date" and then selecting an end date in the calendar that opens (see image below).