Post Process Volume thinks I'm on Mobile?

I’m a complete newcomer to UE4 so please bear with me if the answer is staring me right in the face.

Currently completing the “Your First Hour in Unreal Engine” course in the online learning section of Unreal’s website. It asks me to place a Post Process Volume in my scene and change the min-max values… except the details of my Post Process Volume are greyed out and when I scroll my mouse over the details, it says “not support on mobile, requires computer shader”… except I AM on a computer???

I have no idea where I went wrong (and please give detailed instructions, not just “change setting X and Y”, I need to know WHERE and HOW I can find those settings).

Thank you in advance!