Out of all of the connectors out there the Traxxas ones are the easiest!
The main concept to them is:
1) presolder the tab up to the marked line
2) pretin the wire by applying solder onto it first
3) heat the tab and the wire up at the same time.
4) slide the tab into the connector
Place the tabs on a piece of wood (something that is flat and that can take the heat) with the marked lines face up.