Adding Pictures on Powerpoint Slides

First, find the picture file on your PC using File Explorer. Don’t open it, just press Control + C.
In Powerpoint, Tab to the relevant placeholder and press Control + V.
Your picture will be placed in the centre of the placeholder.
At this point, it is important to think about accessibility.
You can add a description of your picture, for people who cannot see it so well.
You should be focused on your picture when you have pasted it in, if not, you can Tab to the picture.
Press the Applications key (or Shift + F10) for the context menu, Arrow down to Alt Text and press Enter. A side panel opens where you can now type in a description for the picture. There may already be some information there, which was automatically generated by Microsoft. But you can edit it, add to it or, press Control + A then Backspace to remove and type in your own.
When you have finished, press Control + Space, then C to close the side panel.
Note: The accessibility of the slideshow for screen reader users depends on how well structured the slides are and the addition of information like Alt Text for images. This is the responsibility of the slideshow creator.
Follow this excellent link on Powerpoint Accessibility from WebAIM to learn more.