Step 1: Install Hamachi on each computer.
For Windows and Macintosh: https://secure.logmein.com/products/hamachi/download.aspx
(Beta) For Linux: https://secure.logmein.com/US/labs/?wt.ac=73-516-440
Step 2: One person should sign up on the LogMeIn website (this person will be the admin of the network)
Step 3: The admin should create a new network
Step 4: Pass the necessary details onto every person concerned and get them to login (by pressing the power button on hamachi)