You can’t. You’ll need to move to Creative Cloud.
If you bought Creative Suite 6 only (not an earlier version) and probably relatively recently, you may quality to change your license to the other platform:
It is only possible with the Cloud, one of the advantages of the cloud. BTW Microsoft does now the same with their Office 365 and they will also abandon their old purchase model as they told in summer in a meeting in their German Headquarter in Unterschleißheim (near Munich).