I have borrowed this technique from another post, but made it shorter. First, go into terminal and type this:
sudo gedit /etc/rc.local
Insert this at the end of the script, before the exit 0:
ifconfig eth0 up
ifconfig eth0 192.168.2.1
echo "1" > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o ethX -s 192.168.2.1/24 -j MASQUERADE
Where ethX is your wireless card. Reboot.