Don't worry, it happens to the best of us!
Click on the Forgot Password? link from the app's home screen.
More often than not, it isn't the password that users forget, but rather the original email address used to sign up. If you are having trouble with your password, try a different email address first. You may have signed up with a different one and just forgot.
If all else fails, shoot us an email at email@example.com and we'll get you sorted.