How do you find a cheater in chess.com?

1. Check their Elo grow and games. If they all win games as a beginner, that means they are cheating.

2.  Observe their move patterns and their time management.

3.  Check for disconnects, if there is a lot, that could mean there's a cheater

4.   Check there accuracy if the have 90+ as a beginner, that shows suspicion of cheating

5.   Cheaters usually get distracted in games. So check their time management 

So what do you do if they cheat?

Finish the game ASAP (If possible) and use the in-game Report button or the "Help and Support" link (desktop) to flag them and then block the player.

For some more info.

https://www.chess.com/cheating

https://support.chess.com/en/articles/8562517-how-do-i-report-someone

https://support.chess.com/en/articles/8588324-what-happens-when-someone-is-caught-cheating

https://en.wikipedia.org/wiki/Cheating_in_chess#:~:text=Commonly%20cited%20instances%20of%20cheating,by%20the%20rules%20of%20chess

So don't cheat, play it the right way! But if you don't know how to play chess, ask a chess player how to play chess. Good luck!

This isn't the appropriate place for this discussion