How do you sync tabs between computers with Mozilla Firefox Sync?

Mozilla says that with Firefox Sync if you are working on one computer with 5 tabs open you can then switch to another computer or device and Sync can or will update the second computer with those tabs. How do I do this?

BACKGROUND
I have setup Firefox Sync on both devices and they have been synced. How do you sync them again? Is it automatically syncing them in the background? How often? How do you sync the tabs? Are the passwords synced?

Documentation
The documentation below describes how to add another device or computer to Sync. It says that when you add the device it syncs it. But it doesn't describe how and when it keeps it in sync or how to sync the tabs.
[1] http://support.mozilla.org/en-US/kb/what-firefox-sync

2018-05-10 Update:

see this article https://support.mozilla.org/en-US/kb/view-synced-tabs-other-devices

It seems like, you can't see it without logging in now.

The following method no longer works.

Bookmark the following

about:sync-tabs

and use it. Since UI elements have gone as mentioned above and it is only accessible by shortcut (Alt+S+T) or toolbar menu (History>Tabs from other devices)

Tabs from other computers

Update! Mozilla has removed all traces of it!!! It's removed. The following doesn't work anymore...

How to get or show tabs from another computer
In the upper right corner of the browser (Mac OSX, FF10) there is a "List all tabs" dropdown button. It's small and hard to notice without looking for it. Clicking this shows a pop up menu with "Tabs from other computers" (it also contains Tab Groups). Selecting this option shows a new page that has a list of tabs from another computer. Note: I don't remember seeing that option until I clicked the Sync button. I'm not sure tho.

How to sync
• Tools > Sync Now
• You can also right click on the toolbars > select Customize and add the "Sync" button. Hovering over this button shows the last sync time.

In about:config set services.sync.sendTabToDevice.enabled to true. Then right-click on the tab you want to send to another device and use the new "Send Tab to Device" option.