Cannot Modify the Document

[Kyle Blessing]

Howdy, I am trying to create a basic house following some lines, but whenever I attempt to create anything, I receive the following error:

Autodesk.Revit.Exceptions.InvalidOperationException: Cannot modify the document for either a read-only external command is being executed, or changes to the document are temporarily disabled.

I am not entirely sure how to fix this and any help is greatly appreciated!