Create a Petition Page and set it as the home page
1 - Go to + New page in the main menu of your site. Give it a name, change the Status to Published and choose Petition under Type of page.
2 - Go to the page settings and mark the Make this the home page option. This will make this page to be the one that shows when a person lands in your site. Remember to first uncheck all the buttons and check only the "Make this the home page.
After all, it must look like:
ProTip: Slugs are important to keep an eye to. Make sure that they are readable and that are related to the topic of the petition. Keep it short and sweet.