If you installed the latest (12.5, as from 12.6 onwards only HD 5000+ series are supported) Catalyst drivers (aka fglrx) for your graphics card you should already have OpenCL libraries installed on your system.
You should look at OpenCL tutorials (Google is your friend) to learn how to send OpenCL kernels to the different devices managed by OpenCL.
PS: you should really report, at least, what distro you're using and its version. Given that Google is a friend of mine too
, I can presume that you're on an Ubuntu 10.10 machine