Head on over to the Twitterfeed site, click Sign In with OpenID and type in your Blogger blog's URL. Once you've registered you'll then be taken to the New Feed page where you can start linking blog feeds to your Twitter account.
First click the Connect your feed to Twitter Account button, which will prompt you to enter your Twitter login credentials to authorize Twitterfeed's access. You will get a nice little confirmation once you've successfully linked up your Twitter Account.
Next just enter a name for your feed, as well as your blog's Feed URL into the form. If you want to customize your feed's settings you can modify frequency, add prefixes, and even create keyword filters. Otherwise you're all set—click the Create Feed button and your Twitterfeed is enabled.
You can always come back later to the Twitterfeed site and modify your feed settings, as well as look at click-through metrics for existing feeds.