Navigate to MSP Web Console via https://mspbackups.com and login with your provider account.
The Users tab manages all of your users. Here you can see the list of your users, edit them, delete them, and add new ones:
The Companies tab allows you to manage your users and the companies they're assigned to. You can create a company and then assign existing users to this company. Each company gets their own default destination.
The Administrators tab allows you to create sub-administrator accounts that will be able to manage certain companies.