The ATR Stoploss is best used as a trailing stop. While actively managing your trades, move your stops up as price increases/decreases.
There is an offset of 1 candle, so the ATR will only be based on closed candles. This prevents you from moving your stop's when you really shouldn't.
The top lines are used for short positions and the bottom lines are used for long positions.
You can adjust the distance of the ATR lines from your candles by changing the multiplier in the settings. You may want to increase the multiplier to 2-3 on less volatile assets, and keep it ~1.75 for volatile assets like BTC.
Feel free to reach out if you need any tips or more help with using these. Just remember, this indicator should only be used to manage your trades, not enter them.
Cheers.