For the time being you can use IMAP, which is recommended when using multiple devices with the the same account. https://support.mozilla.org/en-US/kb/imap-synchronization

Profile synchronization via Firefox account will be available in a later release.

Thank you for the answer.

I see no-one else has said this but I think it needs saying: IMAP is wonderful for sharing the Emails and whatever folder structure you have created for them but it doesn't share all your other TB settings: address books, message filters, calendars imported/synched and your own TB settings and any extensions you use. I think you can share all these between computers but I haven't yet tested it. I will to remember to update or link here when I have.