Sendible allows you to manage multiple users. Users can be people in your company or your clients. Users can log in and use Sendible themselves or you can manage things for them.
If you haven't previously entered your company details, you will be able to enter them for the first time in My Users.
After adding your details and clicking Save Settings, you'll be able to add users or clients to your account. By default you will be set up as the administrator, allowing you to manage your users and switch between them.