There will be a 'power on' button in the top left, press it. Make sure you download the version corresponding to your operating system. Despite a commercial license being available for purchase, it is not required for use of the program. When you use Hamachi it will be like you are on a LAN with the people the channel you are connected to.
Hamachi is a VPN (Virtual Private Network) application capable of establishing direct links between computers that are behind firewalls, along with various uses such as peer to peer chatting and network chat. Hamachi is an easy way to play Diablo mods online with others.
