To add interactive elements to a form, either choose to edit an existing form or create a new form:
Once in the form editor, scroll down until you see the "Add Item" button:
click to add an item and you will see the new form item where you can change the options to meet your needs:
In the example above the item is of type text, which will allow the user to enter free form information. You are also able to Set the label that will show for this item as well as the default value which will be shown in the entry box.
Below is a list of the other form item types:
The next item which will likely be interesting to people is the Boolean type. This will present the user with a checkbox. For this the only setting you would need to provide is the label of the checkbox.
Most of the rest are self explanatory but the display text will create a block of text to show which the user cannot alter.
You are able to add additional items by selecting the "Add Item" button again and you will need to save the form as you would normally do once you are done.