We do not support the Mac UE4 editor (yet). We will when we have the new Mac-capable IDE. Currently we support the Mac runttime which means that you can only deploy packaged games on Mac.
This is a little tricky and if you don't have a Windows PC to run the editor and SkookumIDE you might want to wait for Mac editor support.
There is still an enormous amount to learn about the editor on its own so you can still experiment with it until SkookumIDE and SkookumScript UE4 editor support is available.