WaveTrend Oscillator is a port of a famous TS/MT indicator. When the oscillator is above the overbought band (red lines) and crosses down the signal (dotted line), it is usually a good SELL signal. Similarly, when the oscillator crosses above the signal when below the Oversold band (green lines), it is a good BUY signal.
I have marked some cross-overs in the above chart. As you can see, they are *not* the only useful signals WT generates. Try it on your instrument and let me know what you think.