Initial setup

1. Download the Firefox ADMX template from our Github page
2. Sign in to Microsoft Endpoint Manager at https://endpoint.microsoft.com.
3. Click Devices then Configuration Profiles (https://endpoint.microsoft.com/#blade/Microsoft_Intune_DeviceSettings/DevicesMenu/configurationProfiles).
4. Click Create profile.
5. Select Windows 10 and Later as the platform and Custom as the profile then click Create.
6. Type Firefox Configuration or any descriptive name.
7. Enter an optional description.
8. Click Next.
9. Click Add.
10. Enter a name like Firefox ADMX.
11. Enter an optional description.
12. For the OMA-URI, enter ./Device/Vendor/MSFT/Policy/ConfigOperations/ADMXInstall/Firefox/Policy/FirefoxAdmx.
13. Select String for the Data type.
14. Copy all of the text from the firefox.admx file into the Value field.
15. Click Add.

Adding individual policies

1. Sign in to Microsoft Endpoint Manager at https://endpoint.microsoft.com.
2. Click Devices then Configuration Profiles (https://endpoint.microsoft.com/#blade/Microsoft_Intune_DeviceSettings/DevicesMenu/configurationProfiles).
3. Click on the profile you created earlier.
4. In the sidebar, click Properties under Manage.
5. Click Edit (next to Configuration Settings).
6. Click Add.
7. Enter an OMA-URI for the policy you want to change.
8. Enter the value for the policy you want to change.
9. Click Add.

All of the OMA-URIs and values for Firefox policies are listed at:

https://github.com/mozilla/policy-templates/blob/master/README.md