To install/upgrade to the LYDIS firmware of a Yealink phone, the phone must already have a version of LYDIS firmware on it.
This means that you cannot from 3CX go from Yealink Firmware to LYDIS firmware. The initial switch must be done by your LYDIS distributor first. What this does allow you though is to maintain you LYDIS firmware up-to-date from the Management Console.
Before someone assumes something, I also want to say that it is Yealink that does not allow the switch from regular Yealink firmware to LYDIS. If you check the Yealink logs when you try to do so, you will see yourself as the log message does stand out.