There are a few ways to create an ADHOC network...
You can do so via Wireless fairly easy with an app called Connectify but since you're attempting to connect over ethernet you're probably going to need to bridge your wireless and ethernet.
Quote:
1. Plug in your pc and allow it to acquiring ip address.
2. click on the Windows button and type "network and sharing center" and enter
3. on the left right under manage wireless networks, should say change adapter settings click that
4. right click local area connection and disable it.
5. right click local area connection and click properties.
6. there should be a tab that says sharing go to that tab.
7. there is a box that says allow other network users to connect through this computers internet connection. uncheck it if it is checked.
8.hit ok then right click local area connection and enable it.
9 now select both your wireless network connection and the local area connection and right click and it should have the option to bridge connections. when you click bridge it will do its thing and should work when its done.
Note: What you should really do is buy a router, but this should fix your problem until you can do that.