DCC ready means just has a DCC compatible connector
You probably have a DC engine without a decoder. Probably paid under $100.00 You will need to consult with the shop owner as to what is the correct decoder to fit inside. DCC ready also does not mean sound capable. Speaker can take up a lot of room, so some engines are sold in one of three ways....1) DCC ready means it runs only on DC as it does not have the decoder board 2) with DCC means it has the decoder board and takes DCC commands but has no sound 3) DCC with sound. Price really jumps between the three levels. Best in the beginning if you want sound to buy it with sound. Adding a basic decoder (not sound) can be really easy when it says "DCC ready" provided that you buy the correct aftermarket decoder, as they come in many sizes and shapes for different engines. A Basic decoder has no sound capability, so when you want to upgrade to sound, you either have to 1) buy a full up decoder with sound and speaker, discarding the old DCC decoder, or 2) if you have bought a DCC sound decoder (locomotive specific), you have to shoe horn in the speaker, which at times means milling the engine body. I should add number 3) buy a sound decoder with speaker....but then you have 2 decoders in the locomotive and that surely won't fit.
So, decide if you want "DCC" or "DCC with sound" and buy appropriately. Good luck. By the way, there are lots of videos on the web on how to install DCC or DCC with sound into specific engines. But for your first DCC engine, buy what you want and buy a DCC ready and don't open it up with the hope of installing a decoder or decoder and speaker.
Welcome to DCC n gauge.