After you complete initial setup for Basic Mobility and Security, you create policies and apply them to groups of users in the Security & Compliance Center. Policies require users of the policies to enroll their devices in Basic Mobility and Security before the device can be used to access Microsoft 365 data. The policies that you set up determine settings for mobile devices, for example, how often passwords must be reset or whether data encryption is required. For more information, see Create device security policies in Basic Mobility and Security and Microsoft Purview compliance portal.
For step-by-step instructions for creating and deploying device policies, see Create device security policies in Basic Mobility and Security.
If you want to exclude a specific group of users from being affected by policies, you can add a group to the exclusion group.