I am testing a deployment of Episerver on Azure and I was wondering if anyone had any instructions or advice on how to active the Relate+ add-on within an instance running in this way?
Relate is not supported when running the solution as an Web App. Please see http://world.episerver.com/digital-experience-cloud-service/requirements/. You need to run the application on virtual machines instead.
Are you just doing a Proof-of-Concept or you already have a project running Relate that you are thinking about putting to cloud?
As Johan said, Relate and Azure are not a good combination. I'd suggest not using Relate, since Episerver plans a different product that will be cloud ready (although ina an early Beta private release) http://world.episerver.com/documentation/Items/Episerver_Social/
If you are already using it, it's a matter of either rewriting it or taking the cost for virtual machines. IMO, rewriting would be a more future proof decision.