Hi,
I don't believe any of the out-of-the box clients (Windows client or eClient, and WEBi) allow you to SET the item level ACL. The clients and API calls will, however, enforce any ACL's that exist on an item. You can use the API to set ACL for an item, the process for which is pretty well documented in the API documentation in the Information Center and in the samples provided in the samples folder of the installation.
Regards,
Javier Plumey
ECM Software Specialist/Architect
javier...@gmail.com
jpl...@us.ibm.com