Okay 
Tappable overlays are just like choices! They’re in the same format; the only differences would be that you need to put the overlay names where the names of each individual choice are supposed to be, and that the word “choice” is replaced with “tappable.” You also don’t need dialogue before it unless you want it. Before you learn how, remember to learn a bit about placing and changing the opacity of overlays if you don’t know how to do those things already; that’ll help