Here is a step by step instructions on how to set up Twitterfeed.

1. Go to http://www.twitterfeed.com/
2. Click Register Now
3. Fill out information Email address & Password of choice
4. Click Create Account
5. Type in Feed Name – This should include keywords from your site
   (Example: Orange County Plumber, Orange County Movers etc)
6. Paste in your RSS Feed URL
   (Blogger: Scroll down to the bottom of you blog and click Post Atom, this is your RSS Feed URL. WordPress: All feeds are blogaddress.wordpress.com/rss)
7. Continue to Step 2
8. Click twitter
9. Now you will authenticate your twitter account
10. Click authenticate twitter
11. You will now be taken to the twitter site input your username and password
12. Click allow
13. Click create service
14. Next we want to set up facebook
15. Click facebook
16. Now we will authenticate the facebook account
17. Click connect with facebook
18. Type in username and password
19. Click allow
20. You now have to select your fan page from the drop down
21. Click create service

Now that you have set up your tweeterfeed account you need to make sure it works properly. Go to your blog and create a small blog post. It will take a few minutes but it will show up on your facebook and twitter accounts.

Here is a great video I found on youtube that will walk you through it step by step.