In addition to a borrower making a reservation themselves, you can also reserve a resource on their behalf, using Circulate.
Select the borrower in Circulate and click the 'Reservations' tab
To make a reservation, enter the barcode number by typing it into the 'Barcode' box. Alternatively, click 'Find...' and select the resource from the list.
The 'Add Hold...' option works in much the same way, but allows you set a specific date for when you wish the reservation to be active from.