[Tristan]

Should be a network icon in the panel next to the date/time. What hardware are you running? What is your wireless card? When I've had issues with wireless cards in the past I've done a Google search to see if anyone else has run into similar issues. There have been a few times where I knew the hardware just wouldn't work with the time/effort I was willing to put in. Luckily, this hasn't happened with any hardware that I own.

Hopefully your wired connection still operates and you have access to plug straight in to a router, etc. If so, you can click on System - Administration - Hardware Drivers and see if Ubuntu finds any drivers for your wireless card.

If it doesn't find any, you can still use windows wireless drivers by downloading from the manufacturer and using ndiswrapper. The operation could get a little more complicated then desired, but searching through the Ubuntu forums really helps in these situations.