Instructions
Insert your "Diablo 2" game disc (or the disc for the expansion, depending on which version you want to play) into your computer. Blizzard Entertainment's "Diablo 2" launcher will appear on screen.
Click "Play" to load "Diablo 2" on your computer. The game's main menu will appear.
Click the "Battle.net" button on the main screen. Type your Battle.net user name and password into the boxes to authenticate your identity and log onto the servers.
Click "Create Game." Select "Open" from the list of options on screen. Fill out the rest of the boxes on screen with the remaining settings you want to use for your game. These settings are left entirely to your own discretion.
Click "Create" to create a lobby for your open Battle.net game in "Diablo 2." When a satisfactory amount of people (based on your preference) join the lobby, click "Start" to start the game.