[Plugin: Ninja Forms] Creating a form before installing add-on

I need to wait a couple of days before I can purchase one of the add-on bundles from Ninja. But I would like to get started now on building the form without having the add-on bundle installed yet. Can I do this? Can I simply apply the add-on (in this case, the Layout and Styles) retroactively to a pre-existing form? Or do I need to wait for the add-on before creating any forms I want to use it on?