The Sintel Forms Designer is the tool that you use to design your forms. Once you have Sintel Forms installed on your SharePoint environment you can launch the Sintel Forms Designer by opening any list and launching it from the SharePoint ribbon.
Once you click on the link from the SharePoint ribbon the Sintel Forms Designer will load and if this is the first time you have used it on the particular list it will notify you that Sintel Forms is currently disabled for the list and you can enable it within the "Settings" screen.
You will notice that the Sintel Forms Designer only has 4 screens namely:
When we were creating it we wanted to ensure that it was as easy to use as possible and require very little training to master. The 4 screens are intended to reflect the logical flow when designing a form from configuring the settings and layout right through to configuring the workflow and finally the logic.
The Forms Designer was designed to be used in a web browser on a PC/Laptop, if you attempt to open it on a device such as a tablet or smart phone you will receive a message informing you to use a PC/Laptop.