turn an estimate into an invoice, you would go through the following steps.
1. Schedule an appointment from the calendar page
2. Check the appointment in
3. Once the appointment has been checked in, you open the Assessment section of the encounter and then click on the "Include Estimated Items" button. This will open a selector which will allow you to select the estimate you created previously.
Once you select the desired estimate, all of the items from the estimate will be added to the current encounter and also to that encounters invoice.