The answer starts on page 3 of "SAS Enterprise Case Management 6.3: User's Guide, Second Edition " which you can find here:
https://support.sas.com/documentation/onlinedoc/securedoc/ecm.html
As an existing SAS ECM customer you can get the access credentials for this secured documentation via SAS Tech Support or on-site SAS consultants.
ECM is mainly used as front-end for some of the SAS solutions (eg. SAS AML). It's not uncommon for bigger sites that customizations have been requested. If you are an end user at such a site then I'd expect there is some site specific user documentation available which you should consult as your starting point.
If you are a developer and this is not just a simple usage question but you need to customize something, then you need to be much much more specific and provide considerably more information.