With Windows 10 1803 knocking at the door, it might be a good idea to start testing it in production. I will show how to enroll one or more modern managed machines into the release preview ring of the Windows Insider Program.

The first step is to register your AAD tenant to the Windows Insider Program for Business. You will need to sign in with a global admin to register your domain.

Second step is to create a security group in your Azure AD and add the machines to this group.

After creating the group, head to Intune, select Software Updates and select Windows 10 Update Rings.
Create a new Update Ring, give it a useful name and click configure settings

Select Release Windows Insider in the Servicing channel.

After creating the Update Ring, assign it to the group you created earlier.

After some time, for me it took about a day, the machine(s) in the group will get a toast notification like this

After clicking this

After clicking Restart now your machine will reboot and if you take a look at updates & security you will see that your machine is already preparing to install 1803.

Have fun testing!