How do I make the files public? I have loaded some pps and some students said they can't open.
If the students are enrolled in the course, then check to make sure that "Files" is visible in the left navigation bar. It should be on by default. The next step is to ensure the file is published. Look at the file in the Files area, and on the line towards the end should be a green cloud. If it's yellow or grey, click on it, and change it to published. Also ensure the class itself is published - that's on the front page of the course, in the top-right corner. It should either not be there at all or say "published".
To Anthony's spot-on advice, I'd like to add a link to the Canvas Instructor Guide lesson we regularly share with faculty at our institution:
Retrieving data ...