In order to print A3 through the college/library printers you need to log into the myPC app which you can find by going to the NCI homepage and under Current NCI Students choose Office 365 MyApps. For the rest of the instructions take a look at this Article.
Please Note: If having followed the article instructions above and the document is not allowing you to change to A3 you may need to make sure you have the Word document set to A3 by choosing Layout and then A3 from the Size dropdown.