hi everyone....not sure if this is the right place for this, but i have a famiclone that is wireless. I wanted to add controller ports to it using another famiclone, but i have no idea how id find out the correct pinouts on the ribbon cables connecting each of the controller boards

i have a multimeter, but tbh i hav no idea how it works even after watching 4 hours of youtube vids ...i never know where to put the black wire lol

im quite good at poking things, so if theres some way i can tell if a button is pressed or some voltage i need to  look for then im open to suggestrions

thanks