If your printer is not on your network but has a screen, it is easiest to follow the instructions with your printer to make the connection via its operation panel. Your Chromebook will detect printers connected via USB as well as WiFi printers already on the network. Select Set up on the printer you are adding to your Chromebook. Scroll to the Print and Scan section and select Printers. Select Advanced, either from the side menu of the settings screen, or by scrolling to the bottom and clicking it.
Select Settings (the gear icon) in the menu to open the Settings Menu.
Click the Status Tray in the bottom right corner of your Chromebook Shelf (the clock area) to open the menu.
