First thing is to install the printer driver software (that came with that printer) on that laptop.

Then in Firefox, you will need to select that new printer in the Printer - Name box at the top of the dialog that appears when you use File > Print or when you do {Ctrl + P}

I will try this soon, do I need to connect any wiring between the laptop and printer ?  :)

What if I do not have (or know where it is), the printer driver software (that came with that printer)?

Download a print driver setup package from your printer manufacturers website.

Here's Brother print drivers:
http://www.brother-usa.com/downloads/

Please note this is a Firefox help forum, and installing Printers is beyond the general scope of this forum. I'd recommend if you need more help with installing your printer, either call a local service shop, or contact the manufacturer of your printer (most printers come with X days of free tech support).