This particular update will be made available to all qualified owners via an over-the-air (OTA) maintenance release from today onwards, so if you hold an Epic 4G in your hands but have yet to see the update arrive, patience is the keyword here. I would recommend making sure you have the Epic 4G on a full battery, since it will take some time to download the update, not to mention a few more minutes for the installation process to be completed.
You might want to check out the forum just in case you run into some epic installation troubles on your, er, Epic 4G.