Read the black jack rules here.
If you want to play, just run the main function in the Boot.kt file.
On the bottom of the current display there is always some information on what you can do next.
Please note, that the special characters for the colors of the cards (♠, ♣, ♥, ♦) are sometimes not displayed correctly on windows. Just use linux or macOs and it should work, or just ignore it, as it is not important for black jack anyway.