I bought CS6 on line. Installed just fine. How do I download a 2nd copy to another location?

What problem are you encountering in trying to download to a second machine?  Do you need a link? You might have one available thru your Adobe account online.  Otherwise you could download the trial version and use your serial number to activate it to full use.  Trial links follow:

http://helpx.adobe.com/x-productkb/policy-pricing/cs6-product-downloads.html

Alternate: Be sure to follow the steps outlined in the Note: Very Important Instructions section on the download pages for the link below and have cookies enabled in your browser or else the download will not work properly.

http://prodesigntools.com/adobe-cs6-direct-download-links.html