There are literally thousands of indicators out there, best to use those that fit your trading style.
Since you're new to trading, might be helpful to start with a few simple indicators and then build your library as you gain experience
For starters, here's a real simple moving average crossover study
It plots an arrow at the last bar they crossed at rather than all the previous crossovers
input price = close;
input length1 = 8;
input length2 = 21;
input crossingType = {default above, below};
def avg1 = ExpAverage(price, length1);
def avg2 = ExpAverage(price, length2);
def lastCrossBar = if avg1 crosses avg2 then barNumber() else Double.NaN;
plot signal = if barNumber() == highestAll(lastCrossBar) and crosses(avg1, avg2, crossingType == CrossingType.above) then 1 else double.NaN;
signal.AssignValueColor(if crossingType == CrossingType.above
then Color.YELLOW
else Color.CYAN);
signal.SetPaintingStrategy(if crossingType == CrossingType.above
then PaintingStrategy.BOOLEAN_ARROW_UP
else PaintingStrategy.BOOLEAN_ARROW_DOWN);
signal.SetLineWeight(3);