Can't load my audios into slideshow on Mac

I click on "add audio." I then click on my computer icon. It doesn't allow me to access all my computer files like I could on my pc. I do put in a folder in "Mounted Folders." But there is NOTHING visible in it. Or any of the other folders in the sidebar. Nothing is visible to select. Just the folder icons themselves. Therefor I have no way to add my audio track.