Why is guiding so difficult? I just don't get it.
Do you have a rotator? If not then just choose External Guide Scope. I am sorry about this, so very few people attempt to use an internal or off-axis guider that I failed to document tjhis. Without a rotator all guiders are treated as a fixed system like an external guidescope.

If you do have a rotator then you have to run through the stuff in ACP Help, Rotator Control. At the bottom of that page it tells how to determine the sensor angle. I won't repeat all of the here.

But for the answer to your original question, go to ACP Help, Auto Guiding your Mount, and click the link at the top of that page Rotated Guiding of Astronomical Telescopes. This engineering paper will explain all of the issues that affect automated guiding of conventional and adaptive optic guiders on fork and german mounts. ACP has to handle all of these configurations.