Please check your Adobe Campaign contract, if your company has bought the Inbox Rendering module. And check in your Adobe Campaign client tool, Welcome>Monitoring page, in the Installed packages sections link, if the package Inbox Rendering appears.
If this is the case, you can use Inbox Rendering at the same place than doing Proofing of your delivery. See documentation for detail. If not, please contact support, perhaps the Inbox Rendering list or the Inbox Rendering Adobe site is not correctly set in your instance.