Be aware that there are only two roles in OMV: admin and user.
As you are configuring OMV, you are in the role of "admin". You managed to setup your first shared folder and share it over the network. So you know now the basic concept of OMV with shares and services. That is something to build on and the next steps will be much easier.
Noted, with thanks.
This now begs the question: How does one login as a user? I've got 2 users and individual passwords for each, but on changing from the system login (user: admin) only appears to give me a screen (via the web browser interface) with a very limited interface (see screen shot below) I'm getting closer to the stage where I'll need to logout as admin and login as a 'user' to operate the system (or am I missing something?).