I would recommend you to install EM 12c Cloud Control and install 12c Agents to manage/monitor RAC databases.
This EM 12c would have centralized repository database wherein all the targets information will be stored.
Install Guide for EM 12c OMS and Agent:
Admin Guide for managing and monitor database targets:
As you are new to EM Cloud Control I would also recommend to go through the Overview of Oracle Enterprise Manager Cloud Control 12c to give you a understanding of the product and its Architecture
Overview of Oracle Enterprise Manager Cloud Control 12c
For new features in 12c
New Features In Oracle Enterprise Manager Cloud Control 12c
Also note DBcontrol would be De-supported after 11.2 release so it would be a good idea to start moving from your existing DBcontrol setups if any towards 12c cloud control
Database Control To Be Desupported in DB Releases after 11.2 (Doc ID 1484775.1)