The SSAO shader is a full screen post processing shader, isnt it?
Well, the usual method to use such a shader is implementing a camera stage; you should find an example in the manual.
I would be careful with it tough; post processing shaders, and SSAO in special, can cause large frame losses;
Oh, and take also a look at shade-c:

http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=273341#Post273341