Can I post a PowerPoint with images found online in an electronic learning environment?

Yes, if you are using the images to explain the educational content. However, a source reference to the applicable guide for the training course must be included, for example APA. If the images are for decorative purposes only, they may only be used with the rightsholder's permission. You may always use images that have been published under a Creative Commons licence or that are in the public domain.

The copyright of the PowerPoint presentation as a whole is owned by the education institution, barring exceptions.