To add the tweet link to your wordpress blog, Edit your Template’s single.php file and add the following code
<a href="http://twitter.com/share?text=<?php echo urlencode(the_title()); ?>&url=<?php echo urlencode(the_permalink()); ?>&via=twitter&related=<?php echo urlencode("coderplus:Wordpress Tips, jQuery and more"); ?>" title="Share on Twitter" rel="nofollow" target="_blank">Tweet This</a>
inside the post loop.
In the code you can edit via=twitter with your twitter handle.Ex.If your twitter username is martin then you can change it to via=martin you can also edit the related account by editing related=coderplus: WordPress Tips, jQuery and more
If you have any queries, leave a comment and i will help you out