Once you know how to solder, you are sooner or later going to need to know how to desolder (more likely sooner than later). Desoldering helps you undo all of those terrible soul-crushing soldering mistakes.
Desoldering becomes an important skill to possess, because you will need to be able to do it to remove the servo controller boards. Removing these boards is necessary in order to build most of the bots.
Fortunately, this is an easy skill to learn!
Step 1: Heat
Go get some desoldering braid and unwind a few inches from the packaging.
Place the exposed desoldering braid over the solder joint on the circuit board that you want to desolder.
Press down on top of the desoldering braid with your soldering iron until you see and/or feel the solder beneath the braid start to liquify and flow.
Step 2: Remove
As soon as the solder starts to liquify, count to two and then remove the soldering iron and lift away the braid by gripping its container (and not the exposed metal braid). The metal is hot, so be careful!
You should see, on the braid, a shiny solder blob. If all went well, the blob of solder on the circuit board is now gone and you can see the freed pin that you have successfully desoldered.
If all of the solder has not been removed and the pin is still attached to the circuit board, simply repeat the process until the pin is free from the solder.
This is the basics of desoldering, in a nutshell.