Changing Ink Cartridge on Lexmark Printer

My question may sound so easy, but I really don’t have an idea on how to fix this. I lost my own instruction manual and I am seeking for one thru the internet. I’m talking about my extraordinary Lexmark printer. Written in front of it is, PinnaclePro901.
The real issue is, I don’t know how to change my cartridges of ink into my printer. Can someone help me on installing cartridge and where to get online instruction manual for this?
I will really appreciate.
Thank you.
