Beat allows you to use simple Git-style version control for your screenplay. To get started, select Screenplay → Version Control.
You are greeted with the Version Control window.

Click on Begin Version to create your first commit. This begins a version control stored inside the document. Your version control information will be kept intact even when saving the file under a new file name.

The small Up to date text at the bottom of the screen means that there are no changes to the document since it was last committed.
Once you do any edits to your document and open Version Control, all changes are highlighted in text view, and the indicator at the bottom now reads You have uncommitted changes.

Click on Commit to store a new version of your screenplay.

The indicator now reads Up to date again. After this, you can compare the versions at the top:

You can return to a previous state as long as you have committed it.