“With your help, we can conduct important tests and address some of the issues we identified during our first Beta Weekend Event. During this event, all you need to do is play normally with a new or existing character on your Beta account using the same game client. Please note that since this is a stress test of our servers, you may experience some in-game performance issues.”
It should be noted that this stress test is only available for those who pre-purchased the game, unlike Blizzard’s open beta stress test weekend for Diablo 3 where it was opened to pretty much anyone with a Battle.net account. If you’ve pre-purchased the game, head on over to the beta forums where you will be able to download the beta client (if you haven’t done so already).