Instructions
Locate your Micro Menu once you enter the game world with your character. The Micro Menu contains various icons, including the "Character Info" and "Dungeon Finder" icons, and it's at the bottom right of your screen by default. If you have third-party add-ons installed, it may appear somewhere else on the screen.
Click the "Play vs. Player" icon, which looks like the horde or alliance symbol and is next to the "Dungeon Finder" and "Guild Finder" icons. A list of battlegrounds will appear in the top pane of the "Player vs. Player" window.
Click "Warsong Gulch" from the list. Click the red "Join Now" button at the bottom of the window. You will join a queue for the battleground. The estimated time you will have to wait will appear to the left of your mini map in the form of the alliance or horde icon. Hover over the icon to view the time.
Click "Enter" once it's your turn in the queue. A box will appear across the middle of the screen with the red "Enter" button. Once you click that button, you will transport to Warsong Gulch.