Alternative text (alt text) is a textual description of an image. According to SpringShare, it's helpful for those using screen readers, mobile devices, or device with slow bandwidth. If images lack alt text, screen readers will not be able to "read" or engage with the image.
When inserting a new image to a page, add the alt text in the "Alternative Text" box field.
Open the editor for the box the image is in. Right click on the image, and select "Image Properties."
Add your alt text in the "Alternative Text" field. Select "Ok." You can also follow these steps to ensure existing images already have alt text.