I believe you need to create a shared network. I don't have cinnamon installed anymore, but the steps are still mostly the same.
Click on the network icon in your taskbar.
Click manage connections
Go to the wireless tab
Click Add, Shared
Create your network with whatever preferences you want. I recommend WPA2 security as it's harder to crack than WEP.
If you want an ad-hoc network instead of a shared network, just click Add, Wireless.
Change mode to Ad-Hoc.
Running on a 4-slot toaster @ 60Hz