Though traffic between you and my server is secure, technically I have access to your minecraft credentials on the server. That is why you generally should not give passwords to unverified sites. However I am passionate about this project and mod and only use your credentials to verify with mojang that you have a legit minecraft account. Your credentials are never saved anywhere on my server. If you are lazy and trust me, use this option. If you don't trust me, which I find perfectly reasonable and take no offense by, you should create an account using the other, more secure, option.
This uses an Oauth procedure to verify your mojang account. You will be directed to the McAuth login page where you have to give your username (not email address!). After that you have to log into minecraft and join the Mc-Auth server. This server will give you a secret code, that code needs to be entered into that login page, this way the login page knows it is you who entered their server. Then you can choose a new password to log into your AdvancedCreation account and you're done. If you want to change your password later just do this verification process again.