2 - Start by "tinning" or applying solder to the posts of the plugs so that they have a good surface of solder to bond the wire to.

3 - Next, cut off only one wire (to prevent shorting your battery) at a time and slide the included shrink wrap down over the wire, moving it as far out of the way as possible.

4 - Splice approximately 4mm of the wire's insulation away and tin the tip of the wire with solder as well.

ADAPT TO ANY SITUATION
With so many types of battery plugs on the market, it's a good idea to build yourself an adapter so you can charge any type of pack you come across. An adapter with your standard "Tamiya" plug, the plugs you use, a plug for micro batteries, and one for receiver packs should cover it. I use a Deans plug as my common plug on the other end and solder each plug to it so I can charge anything, anywhere, any time.

5 - Now, with your plug firmly held in a pair of pliers with a rubber band holding the pliers closed, solder the tinned wire to its appropriate post on the plug. At this point your shrink wrap should be well away from the soldering area to prevent it from shrinking in the wrong place.

6 - Your last step is to slide the shrink wrap into place and, with a lighter, shrink it to protect and insulate the solder joint.

Repeat these steps for the other wire.

Conclusion
See how easy that was? Something to take into strong consideration when swapping out your plugs is polarity. Be sure that your positive lead is always on the same pole from battery to battery and to the ESC. Your newly installed plugs will be more efficient and durable. The ten minutes it should take to complete the above steps and the low cost involved make this the best upgrade you can and SHOULD do.