Login to Oracle Enterprise Mananger Cloud Control 12c console and follow the below steps to install the OEM agent in the target servers.
Step 1: Click the setup menu in 12c OEM console at the right side corner and select the “Add Target” and then select “Add Targets Manually”
Step 4: The host and Platform will display like below, once the entered credentials are correct, you can click the "Next" button to continue.
Step 7: Installation is in progress... (Remote validations and Agent software copy to target server).
Step 8: Remote Prerequisite Check is in progress...
Step 9: This warning is expected and can be ignored. If we have the root privilege you can run the root.sh as root user after the agent installation to fix this issue.