Once you have created a photo essay, you can add one of your photos to it from Profile / Photos. Click the ‘more’ (3 dots) button on your photo, and select add to photo essay from the dropdown.

This will bring up you list of photos essays, you can then check the box of any photo essays you would like to add the photo to. To remove a photo from a photo essay, you need to uncheck the box in the Photo Essays popup.

You can also add a photo to a photo essay from the large popup view of you photo using the more button (3 dots).

You can also add a photo to one of your photo essays during the upload photo process.

NB. You can only add your own photos to a photo essay.