Hold the Spring Carrier in one hand so that you can see the tail of the spring on top, next to the plastic end which you are about to remove.
Next, place the wrench under the spring and hook the single tooth of the wrench onto the tail end of the spring. Let the curve of the spring nest into the curve of the wrench.
Grip the Spring Carrier in one hand and push down while the wrench is still engaged. With your other hand, open the plastic end by turning it counterclockwise. Insert the transmitter metal end first.
Simply screw the plastic end back on the carrier.
Note: for the SC-1.7 model, put the shaft of a screwdriver in the hole in the plastic end to turn it.