The massive patch for StarCraft 2 that will introduce new features and extensions can now be tested on the PTR, launchable through the Battle.net desktop app.
What you first need to do is download the B.net app from here (this is the link for Europe users. If you're from another region, just go to your account, click "Download game clients" and scroll down till you find it), log in and click the StarCraft 2 icon. Above the play button you will see a drop down menu, the top item of which will be the PTR for 2.1. Select it and launch the game.
The patch itself is targeted more at enhancing the StarCraft 2 experience by adding a few features such as:
- Extension mods - a tool to help mapmakers in their mod developing endeavors as well as those players who like to play custom mods themselves
- Clan and groups additions - Made available is a group/clan calendar to better schedule events as well as the option to upload custom decals to show around your command center, hatchery or nexus
- Classic StarCraft 1 soundtrack - Select it by going to options -> sound -> soundtrack and you'll hear the old tracks in any non-Campaign game
- AFK lobby hosts - The game will automatically kick AFK players from lobbies. If the kicked players was the host, the game will promote another player to this position
No information has been given as to when the patch will come live on all servers.
Source: Battle.net
