On the "analyics" tab, I am trying to deselect the aggregate measures tab for an assignment, but my mac won't let me, and I followed all of my instructor's steps correctly. How can I deselect that tab when it physically won't let me?

You can also try dragging a dimension to the marks card like this - you should not have to do that - but it should display an array like shown below (btw it is the way you do a scatter plot on a single or combination of dimensions)

Let us know if that works and please bring it up in your class - if you had problems others did also