LOL ok we will do it this way.
We will assume Aux 4 for your nose steering and Switch A for the gear switch. Switch B is 3 position and that doesn't really make sense for landing gear.
Go into System Setup
Channel Assign then scroll to Next which will take you to input select
Scroll to Aux4 and high light it, move the LTR button to assign the input for Aux 4 to LTrA
Go back to the main screen then go into the Mixing screen
Set up a Normal mix
Rudder as the Master, Aux 4 as the slave
I use 70% both ways for the rate, set these to how much steering you want with rudder input
Trim INH
Switch A
0 is highlighted dark (selected or mix active)
1 is light (not highlighted and the mix inactive)
The end result is when the A switch, or my gear switch is down the switch is towards the back of the radio (away) which is 0, the mix is active and the nose wheel steering is active
When switch A is pulled back the servo centers and nose steering is disabled and the gear retracts
Also, instead of fooling with sub trim or rudder trim, you can us the LTr button to trim the nose steering on the fly without it being tied to a knob or something that can get moved by mistake.