You can manage user access in a variety of ways. Every user can have a username/password required to access the service. This can also be integrated with your single-sign-on (SSO), which is supported at our Enterprise tier.
Some clients want a very low-friction way to grant access, and we support simply sharing the secret app links (similar to a Dropbox or Google drive secret link), so that anybody with that link will be able to access it directly. In that case, only your developers/admins would need to authenticate to manage your account, upload apps, download reports, etc.