ECC Search can be turned on by Business Configuration. Go into your tenant, open a configuration project, and find the BC Scope -> Service -> Complaint Management
Once you scoped in that option, then the work center will appear in your business roles setup where you can add the workcenter to a business role or end user to access the work center.
The Search ECC Documents feature is a top level workcenter so you can search for ECC documents without having to use ticketing.
