First of all have a look on the back side of your laptop, the model number and brand can be found on a sticker via this method. All you do then is put the name and model number of or the laptop in Google search, with the words windows 7 drivers after it.
You will find the manufactures page of the laptop and in a support section for the laptop all of the software drivers needed to be installed for all the hardware fitted into the laptop. IE: the wireless internet a adapter. Download the driver from the site and install on your laptop. Don`t forget you should also have a Ethernet port on the laptop as much as a wi-fi card so if you have a cable to connect it from the laptop to your internet, Broadband router do so to be able to access the internet in the first place to get the wi-fi driver if the wi-fi adapter is not currently working due to the lack of the driver for the wi-fi card not being installed in the first place. It should work ok after that.