In case it helps anyone else, here's how I managed to feed my Nabble forum's content in real time to Twitter.
1. I went to the bottom left of my Nabble forum. I clicked "Feeds" next to the orange icon.
2. I clicked "Topic only" and the document tree is displayed (oddly i had to click a few times to get the tree).
3. On the 7th line of the tree, I found my Nabble forum's feed url. Mine was "
http://sioux-falls-free-stuff.2316505.n4.nabble.com/Sioux-Falls-Free-Stuff-ft4255076.xml" i copied the url.
4. I signed up for "Twitterfeed," which feeds blog's/forum's/website's content to an existing Twitter account.
5. In Twitterfeed, it asked me for my "blog's" feed url. I pasted the url I copied from Step 3.
6. My Nabble forum now feeds in real time (updated every 30-min) to my Twitter page.