Add servers to Central Administration

First, enable the Enterprise Server Option specifically the Central Admininstration Server option in trial and set the server as the CASO server.

While setting up the CASO, you will have the option of setting up the Device & Media, Catalogs location as well.

Once done, install the Managed Media Server option on the remaining media servers. Again, this can be done from the Installation & Licensing - Install Licenses and Options wizard. While installing the MMS, you will have the option of specifying which CASO server to report to.

Would recommend to have a good read at the CASO chapter of the Admin Guide for more information.

This KB article will help as well - https://support.symantec.com/en_US/article.HOWTO99071.html

Lastly, its recommended all servers are on the same version to be managed by the CASO. A lower version MMS server can be managed by the CASO, however its recommended only for rolling upgrade purposes and not otherwise.