The left-hand column of your document editor will contain your Form.
This is what you will use to insert data into your document, as identified when you created the template.
Clicking 'complete form' will isolate the form on the page. From here, you can fill the fields in according to client data. Clicking back on the document or clicking 'Review Document' will populate these fields into the documents.
The form will be broken up into sections as you identified at the template creation stage. As such, your form should be clearly signposted as to where data should be entered.
If you notice any empty fields in the document editor, you can double-click them in the editor to locate them in the form.