You want to sell when the oscillator hits "OVERBOUGHT ZONE" and starts to roll over (red circles and red arrows)

You want to buy when the oscillator hits "OVERSOLD ZONE" and starts to reverse back up (green circles and green arrows)

Generally speaking, every condition is different. 

TSLA, weekly bars

*I like to buy a stock when it hits oversold, and if it continues to decline, i keep buying that oversold condition until it reverses back up.

*I NEVER, EVER, buy after the breakout has already happened and the oscillator at or near the OVERBOUGHT zone (even if I missed my entry)