If a reservation is unassigned, it will show up on your assignments page. To assign a slip or mooring to unassigned reservations follow the below steps.
Go to Assignments page from the left-hand menu on your screen
Click the Assign button next to the reservation you'd like to assign
This will bring you into the slip assignment menu where you can assign one or more slips and moorings to the reservation (Add Assignment from Confirmed Reservation).
Don't forget to click the green save button to the left of the slip assignment menu to save your changes!