The 0 ohm resistor is normally connected to the integrated antenna like this
After making the change to external antenna it will look like this
So the midpoint is the same, but instead connected 0 ohm resistor to the right, it is connected to the left.
On the M7E Sparkfun made it a “bit” more difficult, unless you have a professional soldering Iron. So soldering bridge with a small wire instead of 0 ohm resistor will do the job as well