Go to Network Connections (I usually just click on the network icon, but it all depends on your DE), find your network adapter, Edit, then IPv4, and rather than DHCP in the pull-down menu, choose "Shared to Other Computers". I recommend restarting the system, but you can just disable/re-enable networking, and you should be good to go. Just plug in and go.
Note: I just messed around with this a bit on Maya-XFCE, and I had to do the "Shared to Other Computer" on the NIC going out to the computer (in my case, it was actually a wireless router, not a computer) rather than on the NIC with the internet coming in (in your case, the wireless adapter). There may be some other tweaks you'll need to do, but I've found from my Googling that it seems to be hit or miss. Some people make the one change ("Shared"), while others have to do more. For me, doing the "Shared" thing on my incoming adapter made it impossible to connect to my ISP. Very weird. That's why I did it on the other adapter.