A export box will pop up, click Export in the lower right-hand corner.Click File -> Export -> Export (number) Photos.Press the Command and A key together to select all of your photos.Navigate to the 'Photos' option in the left hand menu bar.Start by exporting your photos from the Photos app. To backup your Photo Library to Google Photos: Backing up your photos is an important step to make sure they aren't lost due to an accident or while your computer is being serviced.