Change document - Order
In order to be able to see this option in Operations first settings in Documents Types Settings have to be done:

1. Creating an Order document
When creating an Order the document is created in POSX form
Program will first ask for a Payment method on Order:

After that program creates order:

Created orders can be seen in choosing option from Operations: Orders overview:

Here a certain order can be selected and with the button Create invoice an POSX invoice is created.