What is the main printer attached to ? Is it attached to another computer via USB or connected straight to the router using an ethernet cable ?
If its connected via another computer then that computer must be on. On that computer go to Control Panel > Printers / Faxes > Right Click on the Printer > Select Properties > Go to the Sharing tab > Select 'Share Printer' and give it a name
Now, go to the laptop and check in Control Panel > Printer / Faxes to see if it now appears. If it does then you should be able to select it from the Print box (e.g. in Word), although it may ask for drivers to be installed.
If it doesn't appear then you'll need to tell the laptop where the printer is. From Printers / Faxes select Add New Printer. Select 'A Network Printer ....' and then on the next page select the second box. In this box you need to enter the printer location like \\ComputerName\PrinterName.