Similar to the above poster: also perhaps check your BIOS to see if there's a setting for the wireless device, like ON, OFF, or MANUAL or AUTO. Change it to ON or AUTO. If that doesn't help, proceed:
It will also usually help to tell us as much as you know about the wireless device you're using. It will help us, if necessary, to make sure you have the right driver for your device, and/or point you somewhere to get
the right driver, although Ubuntu does often have the right driver on-hand. Make and model of the device are a start, but see below:
Is the wireless device USB? Or built in inside the machine? Laptop or desktop?
Please show us the output of one of the following:
For USB wireless device:
For built-in PCI wireless device (we don't need the ENTIRE output -- only the paragraph describing the wireless device if possible. But if you can't tell which it is, post the whole thing):
Note: the `sudo` may be optional - you may not need it.
EDIT: Oh, and P.S. - Please do not post big bright red humungous ridiculous posts again - that's rather rude, and hard on the eyes too. Kindly edit your post and make it a nice normal font & color, or it will be edited for you shortly. Thank you!