Go to:

Apple > System Preferences... > Printers & Scanners > Then click the '+' symbol to add a Printer (see image below).

 > Add Printer or Scanner...

Click on the  button at the top of the window.

In the Address section, type the IP Address for the printer you want. You will need to get this number from the Tech LL. 

As of the time this post was written, here are a few general IP Addresses:

Staff Room Photocopier/Printer: 10.49.162.10

Upstairs Photocopier: 10.49.162.3

In the Name section it will automatically default to the IP Address, but feel free to change it to something you will remember. If you want the official names they are:

Staff Room Photocopier/Printer: P661MFP4

Upstairs Photocopier: P661MFP2

Click Add.

To set your default printer, click the dropdown list beside default printer and select your preferred printer. Done!