EM Database Control or EM Express does not require an additional database, it runs inside the target database and is installed by default. You only need to start the url and connect.
Depending on the DB version the steps may change a bit.
Enterprise Manager Cloud Control is a full monitoring and management application that runs in a separate database and middleware install and uses agents to connect to multiple targets allowing for administration at scale.
Thank you. I just got it up and running, by following a similar document, and with Oracle’s Support.