If you are reading this, you should be a Mac or Linux user. If not, the Windows version is in a different file location.

Things are a bit more difficult for Mac and Linux users, but it should not be too hard.
This is untested, though, so let us know if you have issues.
First, you should go to https://www.tads.org/tads3.htm# and find an interpreter that works for you. 
This is just the interpreter, not the actual game.
Once installed, run the interpreter and open the "Deelzebub.t3" file with it. You should now be able to play the game.

Have fun!