There are two ways to add alt. text to images in announcements.
Option One: Uploading an Image and selecting the "Camera Icon"
Select the Camera Icon
Select “My Computer”
Select “Upload”
Select the Image You Want to Upload
Select “Add”
A Pop-Up Will Come Up Add the Alt. Text in the Box
If the image is decorative, then select the box and you will not need to add any alt. text to the box.