Playtesting is a practice of giving your in-development game (applies to both board and video games) for individuals or groups of people to play so you can learn what works, what needs improvement, how to clarify rules and so on.
Write those notes down. Correct where you need to. And then probably the next night, you’re gonna have to do this whole thing again. And here’s the tragic, heartbreaking part: with a whole new group of people. Because once they’ve seen the instructions, once they’ve seen earlier versions of the game, they are no longer eligible to test a cold read of your instructions. Elan Lee / Board Game Instructions (and why they are the most important thing) by Elan Lee
Board Game Design Lab has a wonderful collection of resources about playtesting at Playtesting - Board Game Design Lab.