The correct steps to be able to display the MDC ID or alias of incoming transmissions is:
Radio Configuration -> Display & Menu -> PTT ID
Check the box for ID Display, It you want it to display while scanning also, check Scan ID Display
Set - End of Voice timer. 0 = id goes away as soon as you stop RXing. 1-7 Sec for staying after Rx stops
Conventional -> Conventional Personality -> Signaling -> Set to MDC. This will need to be done on each personality you want to display MDC.
That is all you need to display MDC as the OP requested.