With the release of iOS 12.2 some changes will be made in the way you install configuration profiles on iOS devices, adding a few simple steps in the process. 

In this example we will use on-device enrollment to outline this process:

After you download your profile you're shown the following:

Afterwards you will have to navigate to the Settings App of the device and go to General > Profile, here you'll see the following:

Click the profile name and you'll be shown the details of the profile:

Press install again and you're met with one final screen:

Press "Trust" and the management profile will install and you're good to go.