What's the best way to write off shares in a bad investment?

Hello, I'm looking for the best way to write off shares in a bad private investment. The only think I can think of is to "sell" them for $0, which I guess will then show up as a loss. Is there a better way? Using "move shares" to remove the shares doesn't sound like the right thing to do. I have the shares in a made-up "brokerage" account. Thank you.