I just extend the steering shaft of the tail wheel up between the vertical fin and the rudder (The hinge line) and with a 90 degree turn in this wire about 3/4 inch long, I stick into a hole in the rudder. So when the rudder turns - the tailwheel turns. The servo turns the rudder.

The tail wheel steering shaft must be centered and in alignment with the rudder hinge line

On a plane with the elevator in the way, I install a piece of 1/8" tubing from the tailwheel bracket and through the elevator to the rudder hinge line. The tailwheel steering wire goes up through this tube. The top of the tube serves as a bearing for the wire before it sticks into the rudder