You can follow the Quick Start guide on the official site.
If you already have an SD card with a working Raspbian OS skip this entirely and start from Install Freedomotic automatically section.
After you have a working Raspian OS you can install Freedomotic on it.
Insert your SD card on Raspberry, boot your system and connect using SSH. On Linux write this on command line
Default password is raspberry.
Open a terminal and copy/paste this command to install and start Freedomotic automatically
sudo curl -s https://raw.githubusercontent.com/freedomotic/freedomotic/master/scripts/installation/freedomotic-raspberry-install | sh
Some things you would like to know:
Java 8 is required and it is available on Raspbian OS by default.
In this example Freedomotic runs with a graphical interface and an embedded web client. If you want to run it in server mode please remove the plugin frontend-java under plugins/devices folder.
To try the web client open your browser and point to http://ip-raspberry:8090. As credentials use admin/admin.