First of all, make sure the wireless switch or key combination is set to enable wireless. Find out what the operating system thinks it is with a command from the terminal ctrl+alt+t:
rfkill list all
If you see any 'hard blocked:yes' then look around the laptop and find and change the switch.
Second, see if you have a wireless interface, ideally wlan0 or eth1:
iwconfig
If you do, that strongly suggests you have a driver installed. Then you should be able to click the Network Manager icon, see your network and connect. If you have an interface but see no networks, check the message log for clues:
dmesg | grep wlan0 <---or eth1 as needed
If not, as we suspect, the next step is to identify your wireless device:
lspci -nn | grep 0280
The pipe symbol | is on the right side of my US keyboard on the same key with the backslash. The device ID, something like 14e4:9876 is key. Use it to search this forum for the method to install the driver and, sometimes, firmware. I suggest Google, searching for the device ID and 'site:askubuntu.com.' Be aware that the method may vary for earlier Ubuntu versions, 10.04, for example, than from the newer versions, 12.04 or 13.04. You will have better results if you include your Ubuntu version. Find it with:
lsb_release -d
Of course, you can ask here if you get stuck.