Each User needs to be allocated to at least 1 user group, and this can be the default Group "Main", there is no need to create more groups if you choose not to. 

To create a user group; Management Portal > Users > Groups > + New Group.

To read more user guide articles, visit the Management Portal > Help > User Guide in your Formitize account or click here; https://service.formitize.com.au/help/guide/ to be directed to the User Guide or on your Formitize App > Help > User Guide.