What you seem to be attempting to do is to make your laptop into a router to route the wireless Internet signal to your desktop. While it is possible, it is in no way as simple as you seem to assume. This is not a simple bridge within the laptop, and the desktop will have very little to contribute, since it doesn't have a direct connection to the Internet. Unless you are doing this as a learning project, IMO, you would better spend your resources buying a USB wireless dongle or wireless networking card which works with the operating system in your desktop.
LMDE Mate 64-bit, LM16 Mate 64-bit
Debian Xfce 64-bit, Xubuntu 13.10 64-bit, Xubuntu Trusty Tahr 64-bit, Antergos Xfce 64-bit, PCLinuxOS LXDE 64-bit