To let the visitors of your site know what content is in each photo album, you can set an album cover. There are a few ways to do this, try and choose the one that is the most convenient for you.
1. Go to Media library -> Click one of the albums below the “Library” button on the left. Click and hold the image which you want to set as cover. Drag it to the right and drop where it says “Drag files here”. The cover image will be now marked with a check mark in the bottom left corner of the image thumbnail.
2. In the album, left-click an image -> Click Edit on the top panel -> Set as a cover.
3. If the cover image is not yet in the album (it’s on your computer), you can upload it as the album cover right away. Go to the album that needs a cover, on the right-hand side click “Upload cover manually” -> Select the file -> Click “Open”. Done!
Setting covers is a helpful feature for pages like portfolio page, where you can show albums as thumbnails, each with its own unique cover.