Bullish Flag is occurred when market moves upward followed by a pause or sideways to lower trading for a few price bars/candlesticks, then market continues to move upward. The flag is usually too short in duration to actually have reaction highs and lows, the price action just needs to be contained within two parallel trend lines.

Draw bullish trend line on chart. It is located just before the flag pattern. Then identify the long candlestick which is similar to a pole. Usually market price moves higher and creates at least the same length as pole