Your Petition Tool would probably benefit from the inclusion of an actual petition, am I right? Tell your supporters what they're signing under the Key Points section of your campaign tool.
You can enter Key Points for your Petition Tool under the Supporter Content section of the tool Content screen:
By default, these points will appear below the supporter information fields on your Petition Tool, but you can rearrange components so that Key Points appear anywhere on the form.
The petition text you create here should look a little something like this:
When your supporters click on that big, friendly Add Your Voice button, they will have taken action to support your campaign. To show them that you appreciate their contribution, you might want to think about customizing your Thank You Page...