The Ambari install wizard attempts to assign the master nodes for various services you have selected to appropriate hosts in your cluster. The right column shows the current service assignments by host, with the hostname and its number of CPU cores and amount of RAM indicated.
To change locations, click the dropdown list next to the service in the left column and select the appropriate host.
To remove a ZooKeeper instance, click the green minus icon next to the host address you want to remove.
When you are satisfied with the assignments, click the Next button.