Indexing a gearmotor with Arduino

I am trying to write a code to index a gear-motor (continuous rotation servo) a set number of degrees with an encoder.

board is an Arduino Mega 2560

encoder has following pins A, A', B, B', Z, Z'
gear-motor has standard servo connection v+, v-, and white

below is the sequence and goals of the program.

1) have a set "home" position that will initially align the mechanism when turned on
2) read state of button, when pressed....
2a) rotate the servo a set number of degrees (360/13) (13...

Indexing a gearmotor with Arduino