https://www.oracle.com/enterprise-manager/downloads/cloud-control-downloads.html
The documentation is currently not available, but I hope it will be published soon.
One of the positive aspects of the new Oracle Enterprise Manager 13c Release 4 (13.4.0.0.0) is, that the underlying Oracle WebLogic Server is now a 12.2.1.3.0 release, not longer a 12.1.3 release :-)
So, happy download and enjoy the upgrade ...