Unlike a regular motor, a servo can only swing back and forth in a semi-circle, 180 degrees. But a servo is also self-aware -- it knows which direction it's facing. That means with a little coding, you can tell it where to turn!
To make the Inchworm crawl, you will program the servo to turn all the way towards the front, and then swing all the way towards the back, over and over. This motion pulls the front and back of the Inchworm together and then releases them, so the Inchworm moves slowly forward.
But before you attach the servo, you have to set it up so that the arm is facing in the right direction.
The battery holder contains your robot's On/Off switch. Make sure to attach the holder with the switch facing out! And position it so the wires face the CPX, since you have to plug them into the JST connector.
Tip: Keep in mind that the battery holder is the heaviest part on the Inchworm. You may want to try sticking it on with tape in different places and giving it a test run with all the electronics working before attaching it permanently.