I did find the instructions on their site, here, a bit crap and instead followed the instructions over here at Blogger Resources
One thing I would add, is make sure, you add <br> in edit html to the natural end of your posts, so it displays correctly. I am not going to go back and do this for all ninety posts on this blog, but I thought I would make sure, my ten most popular pages were formatted correctly.
Check the comments for some advice on how to place this in the date/comment section
Add the following line
tweetmeme_source = 'tweetmeme';
Replacing tweetmeme with your twitter username, so the posts come up @yourusername when tweeted.
Out of interest, here is the countdown to my top ten posts - handy if you are after some hang over sunday reading.