I think you are getting confused by the amp. It has two outputs, but it is still a single channel amp. Both the positive terminals are linked together and both the negative terminals are linked together, effectively giving you only one set of terminals. The reason they gave you two is for convenience, some people use very large speaker wire, and when you parallel it you have to sometimes shove two wires in one terminal, which can be difficult.
Anyway... what I'm trying to say is for wiring in series (what you need for a 2 ohm load) you will only need to use one of the positive terminals and one of the negative ones. It doesn't matter which of the two you use because they are linked together internally.
*edit again* n/m //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif