This section covers who can sign in to an account and what they can do there. Dealers also use it to set up and look after the accounts of their customers.
Everything starts from two entries in the side menu, marked 1 and 2.

A dealer account sells and supports tracking for other companies. As a dealer you:
A consumer account tracks its own fleet. As its owner you manage your colleagues and their roles under Users. If your account has accounts of its own, for example a subsidiary, you also see Accounts > Consumers.

Your role decides which of these screens you see. The built-in Owner role has every permission in its account. Other roles have only what the account's owner gave them.
See How roles and permissions work.