I got a new Fitbit and while setting it up it keeps telling me the email address is already an existing account

Log into your account, go to your user profile and edit your email address, replacing the old one with your new one.

https://help.fitbit.com/articles/en_US/Help_article/1294/?l=en_US&c=Topics%3AAccount_Settings&fs=Search&pn=1#email

Remove the old fitbit:

1. Launch Fitbit from your Home screen.
2. Tap on the Account tab. ...
3. Tap on the device you want to delete.
4. Swipe up to scroll down to the bottom of the page.
5. Tap on the Remove This [Fitbit] button. ...
6. Tap on the Remove This [Fitbit] button in the confirmation dialog.

Instead of choosing "create an account", choose to log-in to the existing account instead.

Best would be to contact your account administrator

In an article titled, "Email already exists," at: https://support.google.com/accounts/answer/69849?hl=en

Google Help advises:
If you see this message when you try to create or change your account username, it's possible that you've already created a Google Account with that username. It's also possible that someone else accidentally entered your email address when creating a Google Account, but was never able to verify email ownership.
To reclaim your Google Account, please follow these steps:

1. Visit the password-assistance page.
2. Enter your username (your full email address).
3. Type the letters shown in the distorted picture into the appropriate field.
4. Click Submit. You'll receive a message at the address registered as your Google Account username. Follow the instructions in this message to reset your password.

After you've regained access to this account, you can either delete the account, or change the username on the account to another valid email address. You'll then be able to change the email address on your other account to this email address.
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I hope this works for you!

Hi , Go to that account , and see if you can get online to finish the app , if you can not get back into it, contact facebook online assist. or email them about the problem , otherwise you are forced to find a new user name .......Good Luck Roy

Get another email address.
http://gmail.com
...is free and has 7Gb, so you can leave it alone for ages and it won't fill up with spam.  Or, you could open an account and in the
Settings --> Forwarding and POP/IMAP
...part, set it so that all emails from your new account are autometically sent on to the address you and your wife share.

If you do open an account; make sure you make a note of the email address and the password somewhere, as it's easy to lose passwords for accounts you don't use often.

Then, of course, you open your facebook with your new gmail account email address.  Job done.

try setting the account up again with the same details but change the pasword
if it says the email address already exists it should come up with the option to reset the password....

If you are using Microsoft office outlook 2007, open your outlook, a wizard will appear, under email accounts click yes,click next, then under auto account setup, click check box on manually configure server settings then next, choose a.) internet email, (if you have your incoming and outgoing mail server), then next, then supply all information needed, account type pop3, name, email address, account name (must be the complete email address) incoming and outgoing then password, then next then hit finish or choose b.) Microsoft exchange (if you have an exchange server and you are on a network or a company) then next, fill out the information needed, your exchange server and your email address then click finish.
If you are using Microsoft office 2003, the process is just the same..
but, if you already have an existing email on your outlook and you want to modify it, go to tools, then email accounts (2003) or tools, option, mail setup, then email accounts, (2007), on the new window, double click the existing mail then supply again all the informations needed: name, email address, account name (must be the complete email address) incoming and outgoing then password. test if successful by sending an email to your own email address