Ubuntu WiFi

Your problem description is too brief, but try the following:

- Check if your wifi is turned on (there should be a button on your laptop)
- Check if your external wifi (usb stick, or whatever you have) is installed properly
- Check your IP address, if its in the same IP-range as your router's
- Check your gateway IP
- If you have access reset your router

It should work so far by now, if not:

- Switch to roaming mode
- Try to connect your laptop through an ethernet cable, if it works find out those settings (IP, gateway etc.) and use them with your wifi thing.

If this doesn't help, there is either a problem with your router or the network must be secured.