Wargames are from the old school era of hacking for fun and keeping things legal. Each level you encounter will get more difficult, and the challenges will push your technical skills to the limit. There are hidden messages, puzzles, vulnerbilities, and cryptography scattered throughout all the levels, so if you do get stuck moving forward, then go back to where it all began. Solve them, and you'll gain access to the next level.
Your ultimate goal is to gain root access on the server. As you progress through the levels run:
touch ~/<yourname>
Once you've completed all the tasks, you'll be invited to the second round of games if interested.
Start here. Good luck... and remember, everything is a clue.