Enter your text to be formatted in the box on the left, then apply an effect by clicking on the appropriate button.
If you want to permanently keep an effect applied to your text, click on the left-pointing arrow between the two boxes. This will copy the text in the output box into your input box.
Once you have finished applying effects to your text, simply highlight the result from the output box, and copy it (Control-C or Command-C).
Note: You can save a snapshot of your text in either box by clicking on the "Save State" button.