The 'Manage Users' tab is where you add all your users in the Private Media Channel. This is where you build your community.
Click on Manage Communities > Manage Users.
Now click on "Add New User" at the top-right corner of your page.
Here you can add in all your user details and even set a profile photo for them.
A Sneak Peek into the Global Role:
Here's where you set the Global Role for your user in the channel. This Global Role is what the user will play for all actions required throughout the channel. So set it right!
Once you have created all your users, their names will be listed alphabetically. There you can click on the message icon to send a private message individually (look at the image, below).
Now that we have created the users, let's go ahead and set the relationship that the user will share with the respective communities that they are a part of.
P.S.: You need to set the role for the user within the channel and within the community first to set the relationship.