1. Go to the page where the form is located. For example the contact page. Every form has an 'edit form' button at the bottom.
2. You will now see the settings of the form. The fields in your form are shown edit them by clicking the "wheel" icon, to add another field click 'insert fields'. Don't forget to click update to save your changes.
3. In the appearance tabs you can find all about editing colors from titles, buttons and fonts.
4. If you want to change the email where all incoming forms will be sent to you can change it here.