Open the Photos app from Applications or the Dock

Find the Photos app and open it. You need to have photos in the app already.

Double-click on a photo and go to Edit mode

Double-click on one of your photos, then click on the Edit button in the top-right corner of the window.

Click on ‘Extensions’ and select ‘More…’

From the items on the right side of the window click on Extensions, then select More…

Enable Super Borders by ticking the checkbox

Enable Super Borders by ticking the checkbox beside its name.

Ready to go!

Once you have completed these 4 steps Super Borders is always available from the Extensions in Edit mode.