You need to set up a device node entry for the printer. Use the following command:
mknod /dev/usb/lp0 c 180 0
Different printer tools are installed with various different rights, and this may affect the access priviledges that you need with the device entry. It is normally correct to make /dev/usb/lp0 rights the same as /dev/lp0, using the chmod, chown and chgrp commands.
You should now be able to use this device in a normal /etc/printcap entry. I recommend use of automated tools to generate such files, such as RedHat's control panel print-tool.I find this driver to be pretty good, although perhaps a bit slow.
If this does not appear to work, check that you have actually loaded the module, and double-check the /etc/printcap entry - especially that the device file matches the one you just created. Also note that some printers require special control characters to be sent to the printer to get the USB interface to be made operational. This is printer specific.