There is no special requirement for DevTest to be able to connect to Oracle 12c - the configuration steps are the same for 12c as for 11g.
There is a requirement for two SEPARATE databases - one for the Enterprise Dashboard, and one for the Registry. The connection details for the Registry can be found in the site.properties file (which also contains the location of the Enterprise Dashboard).
The Enterprise Dashboard is configured in the dradis.properties file on the machine where it is running.
The connections should be configured as per the information in the product documentation, which can be found here:-
https://docops.ca.com/devtest-solutions/10-2/en/administering/database-administration
Note that the configuration is not dynamic - you will need to restart the DevTest components to reflect the new configuration. It is also advisable to delete the lisatmp folder, so the sequence shut-down, delete lisatmp, start-up is recommended.