Of all the connectors I’ve had to make, by far the most frustrating to learn were the DuPont connectors. It took a while for me to figure out where I was going wrong, but once I figured it out, making them got to be a breeze. For something like an R2D2 build, learning to make DuPont connectors is crucial for wiring the servos, the Arduino and all the other microcontrollers used throughout the droid.
I watched numerous other videos when I was trying to learn to make these connectors, but none of them really addressed the specific issue I was encountering, and many even suggested using a sharp implement to help “push” the wire into the connector! What I have learned since then is that unless you are using a thicker gauge wire, you should NOT need any implement to help insert the pin. If you are having difficulty, inspect your crimp and look for damage that is likely causing the problem.
The exact connector kit that I got from Amazon is no longer available, but there are plenty of them to choose from. In addition to the connector pins and housings, be sure to get a decent ratcheting crimper if the kit doesn't include one.