I assume you are talking about soldering the tubes onto the cells? Because soldering the plugs onto the wires is pretty straightforward.
First thing you need is a powerful iron with a big tip. 60W+ makes it a lot easier.
Second thing to do is to tin the cell and the tube.
Third thing to do is to hold the tinned areas together (long nose pliers and a battery jig is a good combo) and apply the iron to the tube until the two tinned areas flow together for a nice strong joint.
It is a little easier to assemble, and fits into some cars better, if you use L-shaped bars on the cells - like these...
http://www.muchmoreracing.com/store/...roducts_id=557
Or, if you don't want to solder any corally tubes, try these...
http://www.muchmoreracing.com/store/...oducts_id=2561