I think that the secret to this is keep it simple and fly it like a Boeing.
Pressing the Appr pb will not work as the guidance doesn't know what approach you want to fly as you have not entered it in the flight plan.
I would fly selected speed as the ground speed mini will not be working correctly due to the incorrect headwind component.. This is why when circling we put the landing runway in the secondary and activate it as you break off the instrument approach.
Go-around will be available and I imagine that the THR Red and Accel (which are modifiable) will be what is in the box.
If it doesn't work select 250kt and pull Open climb and reduce to climb power at the thr red/accel alt