Finish writing your page about Facebook. Include an image of the Facebook logo on your writeup, you may place it anywhere on the post. Press the “Publish” Button when you are done.
After you have published your page, watch this video about making image galleries. Watch this on your computer or phone. You do not need to follow any of the steps. Just watch the video.
Notice the section about the “ALT” field in the video. Whatever is typed in the “ALT” is what tells Google and visually impaired people know what is on the image.