Choose a password that is 6 to 8 characters long, not all letter or all numbers, and not a dictionary word in any language or a permutation of such.
Some examples are available.
Weak passwords are easily broken by intruders with dictionary-based password cracking programs. This is a problem for system security, and thus is not allowed. Accounts with weak passwords will be closed. More information about good passwords is available. We cannot help you without proof of identity.