Maggie, please calm down. If your username or password is over 16 characters, you will need to make a new account. Also check if you typed the password and username correctly, using no symbols in your password. What does this error say? It would help a bunch if you told us.
Maggie, please explain what's the problem. Nothing you say makes any sense. Please be discriptive, if you won't, we will not be able to help.