Firefox Sync works by storing your data on Mozilla servers and synchronizing it with your computers and devices. When you set up Sync, you enter an email address and password in order to prevent others from accessing your account. In addition, we encrypt your data with a key derived from your password in order to keep it safe on the server. This article explains what to do if you forget or lose any of this important information and are unable to access your Sync account.
To get a new password follow these steps.
Now you're ready to go. Remember to update your password on each of your synchronized devices by following the steps below:
Unfortunately there's no way to change or recover the email address associated with a Sync account. You would need to create a new account following the steps described in How do I set up Sync on my computer?