In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
In the OptionsPreferences window, click on the Sync tab.
Click Set Up Firefox Sync
Click I Have A Firefox Sync Account
Enter your Sync email address and password and then click Next
Enter your Sync Key and then click Next
Your Sync Key is a long series of characters that was created for you when you set up your Sync account. You can find it by following the instructions in Where can I find my Sync Key?
Your Recovery Key is a long series of characters that was created for you when you set up your Sync account. You can find it by following the instructions in Where can I find my Recovery Key?
You will see a Setup Complete screen. Click Finish to finish adding this computer to your Sync account.
and select .
In the OptionsPreferences window, click on the Sync tab.