You can use the "BollingerUpper" and "BollingerLower" functions.
The syntax is:
BollingerLower(series, number of Std Devs, window) BollingerUpper(series, number of Std Devs, window)
Examples for sek:
BollingerLower(sek, 2, YearLength()) BollingerUpper(sek, 2, YearLength())