As wifi issues crop up a lot on linux, I have put together a bit of a guide on common troubleshooting steps (including Additional Drivers as @Ponce-De-Leon already mentioned) and advice on what information to provide in your posts to try and help others help you quicker and more accurately.
(please don't reply to that tutorial with your information, post it here)
A key thing would be to know exactly what wifi chip is in your machine (if integrated) or what wifi adaptor dongle you're using (if a USB thingy). If it's integrated but you're not sure what the chip itself is, please provide the exact make and model of your laptop, or desktop motherboard, or whatever device it is you're using.