You can get to the Lend screen either by clicking the Lend button in Circulation
After selecting a borrower you will see the Lend screen...
If you right click on a resource in the Current Loans area, a menu will appear
Click on the Extend loan option in the pop-up menu and the Extend Loan screen will appear just as it would if you had used the Extend button on the front screen
If you hold down Ctrl and click several resources in the Current Loans area (or use Shift and the Up or Down arrows to select several items) you should use this Extend Sel Loans button to grant a bulk extension
Remember: It is a good idea NOT to grant extensions unless the borrower actually presents the resource for an extension!