I recently bought a flysky it4 and am trying to setup my 3ch transmission shifting and the 4th different locks, I have already bought the diff lock controller thingey, but I do not know how to set them up. When I go into servo setup it tells me to press the servo interface button, and then I don't know what to do. Anyone with a flysky it4 or knowledge about the system pleasettings help. P.S when I press 3rd channel it goes to the other endpoint but then returns to the first one once I let it go.

Thank you