Use the RSI's own smoothing setting. Relative Strength Index (RSI) can draw a moving average of the RSI line in the RSI pane.
- If the RSI is not on your chart yet, click Indicators or press
/, search for "rsi" and click Add on Relative Strength Index (RSI). - Hover the RSI's legend row and click the gear.
- Under Smoothing, set Smoothing Type from None (the default) to SMA, EMA, RMA, WMA or VWMA.
- Set Smoothing Length to the average's period (14 by default).
Pick SMA + Bollinger Bands to draw bands around the average as well.