* I added a button to my course, but my students can't see it.

When you add a button to a course, by default it is created as "unavailable."  Be sure to click the "available to students" checkbox before clicking "Submit" when creating the button.

If you are creating a content area, students will not see the button until you add your content.  Click on the button to open the content area, then click on "Build Content" to add items.