How to do 2D integration with ROOT::Math::IntegratorMultiDim

I want to integrate a 2D function with parameters. I have defined it so that I can construct a TF2, but the Integral method of TF2 is not working to my satisfaction. I have found the ROOT::Math::IntegratorMultiDim class, but cannot figure out how to pass my function so that it works.

Note 1: this is a follow-up question for Why is my integral zero? where also my function is attached

Note 2: the problem is probably my subpar programming skills, so any “dumbing it down” will be greatly appreciated!

Edit: I think I got it now!