Once an admin account is created, you can go ahead and onboard your users. As described in the article Setting up a team you can onboard your users in the following ways:
Dispatch individual email invitations
As the admin, log-in to your account on drive.explaineverything.com, go to the My Account page where you can access the User Management panel. There you can invite users by providing their individual email addresses (or uploading CSV with a list of your user's emails).
Share invite code
Codes can be used to invite users to your existing Team. You can either provide a general code that allows anyone to register & join your group or, alternatively, you can preconfigure accounts and provide individual codes to each user.
Deploying preconfigured apps using MDM
If your users will mainly use mobile apps that are maintained using an MDM system, you have the possibility to preconfigure and deploy the app to your users' devices. Please follow the instructions from the article App deployment with use of MDM solution.
Users self register through a whitelisted email domain
Whitelisting the email domain (or set of domains) allows users to simply use their organization's email to register. They will then automatically be added to a Team. See the article Whitelisting your domain in order to do that.