How Do I Become a GSX Administrator for my Company

I completely realize this is probably the wrong place for this post, but I have no idea where I should go.

I currently do all the tech support for my company, as well as outsource to a couple of "travel to your office" support companies. And as such, I would like to have official access to the GSX, but I am having difficulty finding that specific information in EN-GSXUserGuide.pdf.

When I log into the GSX site, I get to the point where I am asked to enter "Please specify Sold-To Account # :", but I don't know what it is and where to find it, or how to acquire an account.

Currently, we do not have a GSX Administrator, as that would be my job.

Can anyone tell me where I should go to follow up for detailed info, or what the steps are to acquire a "Sold-To Account #"?

TIA
Gary