Thank you for your post.
1. Pull down the View menu and select "Layout Mode".
2. Pull down the Layouts menu and select "New Layout/Report..."
3. Give a name to the Layout (Invoice?), select "Blank layout" and click "Finish".
You are now presented with a blank screen to do what you want.
Click on the Text tool and type "INVOICE" near the top of the page. Feel free to change the Font, size, type, etc.
Using the Field tool, place the fields you want on the invoice. Format the fields the way you want.
This should get you started in the right direction. Let me know if you should run into any difficulties.
Here is a beautifully simple demo by Comment which shows proper structure with Contacts, Invoices, LineItems and Products. If you structure your base solution this way, you can't go wrong. http://fmforums.com/forum/showpost.php?post/309136/