In the upper right of virtually every screen in FTM is a "Share Button". Clicking on that Share button allows up uploading a copy of that FTM file to ancestry.
This was the way to upload before sync.
The normal way of uploading if FTM was your primary data entry point used to be (and still is for many) doing this periodically (weekly, monthly, as needed). The disadvantage was/is each upload is a separate file with a different URL than the previous one. Invitees to your file have to be notified of the new upload. If people have bookmarked a specific url of ancestry file and you delete the old one, their bookmarks no longer work.