Guide: http://code.google.com/p/robotframework-ride/wiki/InstallationInstructions#Robot_Framework
In ubuntu11.04, we only need to install robot-framework, xyPython, and ride.
Step1. Install robot-framework
Guide: http://code.google.com/p/robotframework/wiki/Installation
Step2. Install xyPython
apt-get install python-wxgtk2.8
Step3. Install ride
download and tar the tar.gz package, and type python setup.py install
Now you can type ride.py to startup the IDE(need to use root).