Hit the Command and A key together to select all of your pictures.Find the folder where you exports all of your pictures from the Photos app and select it.In the top right section of the window, click the "Import" button.Sign in (if you aren't already) and click continue on the information box.Open your preferred browser and go to "".A small circle will appear next to the photos button in the top of the window.
(Please note that for large photo libraries, this could take a long time.
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.