After you have successfully installed and activated Form Builder plugin, you can create as many different forms as you wish. Just open Form Builder, click "Add New" and then give you new form a name.
When the form is created you can add various fields to it. To add a field you need to choose the needed input type from a dropdown, then click "Add filed".
After the field is added you may name it, set it a required one, add field description, set validation type for it, name fields like radio buttons or checkboxes etc. If you need to reorder your fields, you can drag-n-drop them like shown on the screenshot: