Instructions
Open the "StarCraft 2" game launcher. Sign into your Battle.net account when prompted.
Click the "Multiplayer" tab in the upper left corner. The multiplayer interface will appear in the middle of the launcher window. Find the "Custom Games" section in the lower right corner. Click "Join A Game." A list of all available games using custom maps will appear.
Type "StarCraft Universe" into the search field in the upper right corner and press Enter. A list of available games will appear. Click on any one of the games. Click the orange "Join Game" button below the search results. The mod will begin to download instantly. The download progress will appear just below the "StarCraft" logo at the top of the screen. Once the download is complete, the map will be installed on your system and you will instantly join the game. You can then create games using this map at a later time.