Lethal League is a competitive projectile fighting game where you have to hit an anti-gravity ball into the face of your opponent to win. The ball speeds up with every strike, up to explosively extreme velocities. Play intense local matches with friends and foes, challenge yourself in the singleplayer mode or battle it out online.
Go to: http://store.steampowered.com/ and download STEAM client
Click "Install Steam" (from the upper right corner)
Install and start application, login with your Account name and Password (create one if you don't have).
Please follow these instructions to activate a new retail purchase on Steam:
Launch Steam and log into your Steam account.
Click the Games Menu.
Choose Activate a Product on Steam...
Follow the onscreen instructions to complete the process.
After successful code verification go to the "MY GAMES" tab and start downloading.