There are basically three way of installing Contiki and getting started:
- Download Instant Contiki 
- Download ContikiOS from Sourceforge repository 
- Clone ContikiOS from Github repository 
Installing Contiki using Instant Contiki
This is the easiest way of installing and using ContikiOS. You simply need to download Instant Contiki, which is a virtual machine created with all necessary toolchains and software for Contiki development.
Link to download Instant Contiki: 
After downloading Instant Contiki you need also to download either VMWare Player or VirtualBox, if you are using Windows as your host OS. If you use MacOS X you should download VMWare Fusion, instead of VMWare Player.
IMPORTANT: To login in to Instant Contiki: username: user passwork: user
Installing ContikiOS from Sourceforge repository
First step consists of downloading ContikiOS and unzipping it inside your preferred folder.
<CSO_Source>c test </CSO_Source>