Hi, I trade using the ATR. To see it on a chart, I use TradingView (free version) and I've added the "(mab) ATR Band" indicator to my chart. It's very helpful for seeing the boundaries of the ATR. The indicator is dynamic and changes throughout the day with prices. This prevents me, for example, from taking a short position when the price is already close to the lower limit.
For the calculation check this article : Average True Range (ATR) Formula, What It Means, and How to Use It (investopedia.com)