Trend line strategy is actually a simple one, you pick a trend and use the trend line tool to draw a line to touch the wicks of the trend.
If it a downward trend, the trend line has to touch at least two wicks on the trend to be credible.
Now, after you have gotten your trend line drawn, the idea is that price will not break above the trend line so you can set your Stop Loss above the trend line for safety.
Whenever price breaches the trend line by about two candles, the trendline is nullified.