Ok,
VV32 is the trans. to automate the create of the output message from invoice (there is also VV12 for sales, VV22 for deliveries ..)
Here, you could chose for your sales organisation 1100, for each customer number how to print your invoice. You have selected a key very low level, I'm sure before this screen you could chose another key level in a pop-up ??
after you select a good key level, you could specify the function partner (ship-to, sold to party ... ) if you want to print, to fax, .. if you want to print immediatly .. (you will need to press the communication button for printer details)
After you do this and save it. Next time you go in an invoice, correspond to the key you have created, if there is not already an invoice message, SAP will create it.
regards
Fred