If when you attempted to home the machine, the machine only moved down a bit, you will first want to shut the machine off for 30 seconds and turn it back on to reset it.

With the machine back on, manually raise the carriages to the top of the machine so the carriages are near the home position. See pic 1.

Click the knob on the LCD and go back to Advanced menu and click the knob. Then scroll to Calibrate Z Height and click the knob.

On this menu go directly to Z Position and click the knob. See Pic 2.

Now scroll the knob to lower the carriages down to bring the nozzle closer to the bed.

When the nozzle is close to the bed, click the knob and go to Set new Z=0.00 and click the knob. The LCD should beep. See Pic 3.

Now scroll to Home towers and the machine should now be able to home to the top of the machine properly. You can now move to the next step.