How do I change the photo album cover?

On the main photos page, you can have Photo Albums. Each album can have a 'cover photo' that covers the whole album block:

To change this image, click into the album you want to change. In the top right corner look for a button that says 'manage.' Tap that.

If you have not set an album before it will look like this:

Click on 'Select a Photo' and you will then get a list of all the photos in that album. Click on the album you want to use. When the page refreshes, it should look like this:

 You can click the 'Select a Photo' button to select a different one, or hit remove to unset the album photo. It will not delete the photo from your site, just remove it as the cover.