transmitter receiver binding

I have been trying to bind my Radiomaster R88 to my Radiomaster Zoro and can't seem to get it to work. It's my first time trying to do this, so all help would be appreciated.

I power on my servos and they go to, what I assume is, the center position. But, when the radio connects to the receiver, the servos change position. I am not sure which is the actual centered position. I don't have one of the servo tools that let you run through the whole range of motion, but...