Look for customers, drop down to create invoices,
You will need :
Customer name & address
Item that you are selling as well as its category - is it a physical item or a service?
The price of the item sold
The freight or shipping if any
The terms for payment ( upon receipt, net 10 days 30 days etc)
and there is a place for a company message ( thanks for your business etc)
QuickBooks offers standard templates in the Create invoice window or you can create your own customized format
No matter what you sell or who you sell it to, Your compay information should be accurate in " My Company" before starting - name address, phone/email/fax as well as an optional digital art logo.
If you need help beyond this I would be happy to walk you through the setup & steps.