Plugin and turn on the printer.

Using the screen menu, move the X axis up until it crashes in to the Z tops. The stepper motors will skip, making a noise - this will not damage the motors.

If your printer can't reach the Z tops, unplug the printer and plug it back. You can now reach Z tops.

Using the screen menu, move the X axis down until the nozzle is approximately 10-15mm from the heated bed.