Stop loss is use to minimize the loss you could suffer just in case the market went to the opposite direction of your trade, because it will stop your trade once it’s triggered on a certain price you’ve set it.

If I’m not mistaken, it’s always visible on the trading panel in futures, you just have to explore UI of whenever platform you’re using in trading. If you can’t still see it, for sure there’s a lot of YouTube tutorials regarding about the exchange where you’re doing your trades.