when you installed flexi,, didn't you get a set up screen to add yoru printer?
If not go into production manager and add one in,, yes?
I am no flexi expert.. but this is how i could do it.
type in some numbers,
this will bring up the cuttter and printer icon on the tool bar.
click the printer
brings up production manager
then install your printer..
Not sure if this is exactly what to do,, but it should get you started.