Run the scripts with your best guess for the X and Y offsets. When you run the X calibration, your X offset is correct if the center (longest) line is the straightest. If it's not, find the one that is straightest and count how many places from center it occurs. Add [increment] for each place to the right of center, or subtract [increment] for each place to the left. If none of them line up, try a larger increment to get a better offset estimate, then generate the test pattern again with that value.

The generated gcode does not contain warm-up codes, so you must set the temperatures manually and make sure both extruders are up to temperature before starting.

To calibrate Y, repeat the process with the Y calibration script, adding [increment] for each place to the back of center, or subtracting [increment] for each place to the front.