(be sure to replace 'your_twitter_name' with your twitter user name)
then click 'Done'
To Customize the 'Tweet' Button
You can add certain modifiers to the tweet button to change the default text included in the tweet. For a full list of possible modifications you can make to the tweet see Twitter's Tweet Button page. Here are a few key ones:
data-url will change the default URL included in the tweet
data-via will change the user name included in the tweet
data-text will allow you to edit the text included in the tweet