To add alternative or alt text to a slide, so that it can be read by assistive technology, you would enter a short sentence describing the slide in the Slideshow Administrative here as shown in this screenshot:
- Click on the pencil / edit icon.
- Enter a short sentence that describes the slide and what will happen if you have enabled the link.
- You may need to click on Save between actions, that is, updating each of the slide fields of information.