How to add Tweet button to all posts

[sponzertgmailcom 0]

Hi, Can anyone tell me how to add a Tweet button to each post i make? If you don't now what i mean, take a look here. I need tp lace a small piece of code somewhere but have no clue where to place this code. This is a example code:

Tweet<script type="text/javascript" src="http://platform.twitter.com/widgets.js"></script>[/code]