Setting up AD-HOC network

Hi all

I am trying to set up an AD-HOC network on my MBP running on Mountain Lion.
Doing this because my iPhone needs it to get on my Wi-Fi network.
I already have a Wi-Fi network, which demands a login, and only allows one connected device at one.
This Wi-Fi is set up by my Time Capsule.
I literally have no idea how to set up this AD-HOC so your help is much appreciated, so I can use the Wi-Fi on my iPhone, too.

Thanks in advance

 

No one?