I can't even see an option for printer type, where usually Fax, Windows, IP buttons are (toolbar on the top). See picture.
How is that possible and how can I add printer manually by IP?
OK, so this is not really an answer to the questions why you can't do it. But this should allow you to install a printer:
open safari and go to
that is the CUPS web interface for your local printing system. you should be able to do things like adding a removing printers in there. if it tells you that the web interface is disabled open a terminal and type: