Adding a real money store to game

I haven’t found anything in search that goes into detail, or gives a tutorial on adding an in game store to your UE4 game.

Any post about it has users just saying, use a variable of currency where it’s checked if the owner can pay for the item, connected with 3rd party pay system,
But doesn’t say how? Anyone know how, exactly?

Mobile or some other platform?

​computer …