I'm not really sure how to play.

Unfortunately I agree with @NinjaNic, the game is very confusing. I don't understand much either.

The background is confusing, I'm not sure I understand what the rectangles are (are they troops? Why are they spread out? Why do they move randomly?). What does it mean to retreat to safety? What should I do after I win? The game could be improved to guide the player more. In the current state it's not very fun.

Kudos for making this using Scratch (Code Club!)
I figured out how to play by "reading" the source code. I moved my little black square over the red square (the tribespeople), pressed E a few times, then "The enemy falls in the field. You are victorios (sic)".

Interested to know if you're using this as a teaching tool, etc.

This one was a bit confusing, maybe add some directions. I'll be sure to replay if you add some.

Interesting game, but I wasnt sure what to do? I included it in my compilation video series of all of the MiniLD 69 games, if you’d like to take a look :) https://youtu.be/fqpIvqrRLGw