Bachmann EMD FT-A loco

[LocoJon]

This engine comes DCC ready, but has no place to plug in a sound decoder.  How do I add sound to this engine?

[ABC]

This engine comes DCC ready

No it doesn't, no Bachmann FT-A's are DCC ready they are either already DCC equipped/on-board or are just DC.
I have several FT-A's and I have noticed that there is not enough room for a good speaker and baffle, so unless you are prepared to do some milling and reconfiguration of your loco...you will either have very poor sound or you will have to live without sound (or buy a loco from another manufacturer with sound).