The bad part of that screen is they have built in a bunch of their own routines, and gcode pings to the board it is connected to. Normally that would be awesome, but the firmware has that stuff scattered over hundreds of files so it is not easy to find and edit. so using that screen stock you will see all sorts of random errors pop up, but are mostly meaningless since we are not 3D printing.
So using the home Z button should kinda work, but really the better way to do it is just build it into your gocde. If you have a look at the milling basics page you will see how I do it. I home xy then move to the material, probe Z, offset Z, move Z, pause for probe removal and so you can turn on a router, and you can resume from the TFT Touch side. Once you have the routine you want/like you just add it to your CAM start gcode and tool change sections. I am pretty sure I show me using it in one of my latest youtube clips.