In order to run FireCMS, you need to create a Firebase project first, with some requirements:
You need to enable Firestore in it. You can initialise the security rules in test mode to allow reads and writes, but you are encouraged to write rules that are suited for your domain.
Note that you can also link your new webapp to Firebase Hosting which will allow you to deploy it with very little effort. You can create the Firebase Hosting site at a later stage and link it to your webapp.
You will most likely want to enable authentication in order to pass the login screen
In case you want to use the different storage fields provided by the CMS, you need to enable Firebase Storage. The default bucket will be used to save your stored files.