I've requested the certificate and now I want to complete it within IIS. I'm getting an error, though:

"There was an error while performing this operation. Details: Access is denied. (Exception from HRESULT: 0x80070005 E_ACCESSDENIED))"

This seems like a permissions issue. Are you logged in with administrator credentials? Are you using IIS Manager to process the certificate request? Could you share what version of Windows this is on?