Use the username or email and password from your sign-up email.
Choose a new password for your account.
This is the name shown on every leaderboard.
You sign in with this name too, so use the new one next time. Your email address always works either way.
Sign up to follow matches and get result alerts.
Create a league, invite your friends, predict match winners and exact scores, and climb the leaderboard. Lock your picks at least an hour before each match — once locked they're final, and you'll only see everyone else's picks for a match after you've locked yours.
Run a competition your own team plays in. Pick the format, invite teams, and let the bracket look after itself — results are checked against Dota's own match history.