Try typing stockfish into your terminal and hit Enter and see if the program loads. If it does load and run OK from there you should be able to create an XFCE whisker menu shortcut for it with just the command stockfish.
TC
entered the word stockfish and pressed enter. then only the following line appeared
Stockfish 7 by T. Romstad, M. Costalba, J. Kiiski, G. Linscott
nothing else happened??
Bit of advice; when downloading software in compressed format i.e zip, gz. after decompressing a good practice is to read the
READ ME file which among other things explains how to configure, install, run and use the program/software/tool/app. I downloaded stockfish, decompressed it, followed that very same advice I just gave you and found this very intersting information you obviously missed:
Stockfish is a free UCI chess engine derived from Glaurung 2.1. It is not a complete chess program and requires some UCI-compatible GUI (e.g. XBoard with PolyGlot, eboard, Arena, Sigma Chess, Shredder, Chess Partner or Fritz) in order to be used comfortably. Read the documentation for your GUI of choice for information about how to use Stockfish with it.
Next time take a look at the READ ME file and save youself and others time and trouble. On the other hand, as I was reading that READ ME file I couldn't help but notice that stockfish looks like it might be quite difficult to set up. If you want to play chess in LL it might be better to look for one in synaptics; open menu, type synaptics in the search bar and hit enter, a dialog box asking to type in your password shows up, type it in and once synaptics open, in the search bar type "chess" and navigate throught the resullts till you find something.
Also
apt search chess
shows:
3dchess/stable,stable 0.8.1-19+deb9u1 amd64
Play chess across 3 boards!
brutalchess/stable,stable 0.5.2+dfsg-7 amd64
3D chess game with reflection of the chessmen
dreamchess/stable,stable 0.2.1-RC2-2+b2 amd64
3D chess game
and a few others. You could install one of those by typing in the terminal
sudo apt-get install 3dchess
type your password when asked, press enter type (Y) when asked and wait till the install process finishes, once it does try your game and tell us about it.
Hope this helps!