Despite the constant marketing to the contrary, mobile devices can remain perfectly capable long after their launch dates.
They can, however, start to seem a little slow or behind the curve after a few years of use — and the older and more resource-limited a device is, the more pronounced that effect is likely to be.
Lots of phones have limited local space, and clearing out the clutter can go a long way in making things run better.
Tap the menu icon in the app's upper-left corner, select "Settings," then select "Back up & sync" and activate the toggle that appears.
(If the toggle was already activated when you got there, congrats!
Follow the steps to set up syncing and then wait while Photos backs up your entire image and video collection to the cloud.