Hi:
The use of stored processes in Web Report Studio isn't much different than the use of stored processes in any of the other client applications. The only thing to really note is that the output type of the Stored Process is SASReport XML -- and not HTML, CSV or RTF as in some other client apps.
The use of report parameters to prompt the user for information prior to running the stored process will be the same in WRS as it is for the other client apps, too. Once the parameters are defined in the metadata, then the prompting interface is generated by each client application to gather input from the user.
These papers talk about stored processes and parameters:
http://www2.sas.com/proceedings/forum2008/024-2008.pdf
http://support.sas.com/rnd/papers/regional07/paradigm_edu07.zip (zip file of programs for above paper)
http://www.nesug.org/proceedings/nesug07/ap/ap22.pdf
http://support.sas.com/resources/papers/proceedings09/330-2009.pdf
Depending on whether you have SAS 9.1.3 or SAS 9.2, the documentation is your best resource. But look at the version specific doc, you have the ability to create cascading and dynamic prompts in SAS 9.2 and those will not be in the doc for SAS 9.1.3.
Generally, when speaking of filters, I think of filters on an Information Map. You can also populate a stored process with data that comes from an information map that is linked to the stored process. That type of filtering is described here:
http://support.sas.com/kb/26/175.html
For more information about other types of filters with Information Maps, look at the Information Map documentation.
cynthia