When you create a new element type the only property it has assigned to it is "Name". As you link element types together through connection types, the element types will automatically have fields added to them for capturing these connections.
These auto-generated fields make it very easy to get started using your model, but often you will want to add additional properties to the element types you create, or edit the auto-generated properties.
You can describe your elements in more detail by adding fields to their definition. Hover over the element type and click the "Define" icon:
You can rename and edit fields that are already there by double clicking on them. You can click the "Add" button to add additional field of different types: text, images, video, even document uploads.
As you change your element type's definition, the system will be auto-generating a data entry form for you. Save your new definition and then try to add data by hovering over the element type and clicking "Add". You'll see a form based on your definition:
Even if you're planning to upload data in bulk, it's convenient to use the "Add" feature to check that your definition is as you want it, and it's a good idea to manually enter a few elements manually to make sure your model is acting as you expected.