The Celeste has been sampled and the wav files used to create a library that loads into a free VST sampler/plugin called Decent Sampler which can then be used in a DAW, or other vst host or as a standalone instrument on your pc.
When correctly set up, you can attach an external keyboard to play the library or use a pc keyboard for limited control or use it in a DAW with the mouse.
It might sound complicated if it is all new to you.
The easiest way for you to start is to search out Decent Sampler at decentsamples dot com. You need to register a free account to use it, so click on My Account at the decentsamples site.
Then download and install Decent Sampler. Too tired to add much more. See how you get on and post again if you need help. No doubt someone will link to a suitable video to explain it further.
Good luck and have fun.