When its bullish does that mean I can buy?
When its bearish does that mean I can sell?
Bullish and bearish are price movement trends, that can either be bought or sold, e.g. price is moving up - bullish - you can buy or sell depending whether you think the market will continue to rise or be ready to fall.
Hence trend traders will follow the trend.
Yes the main idea behind them is buying and selling. But each candlestick pattern comes up with more factors that you need to follow and read thoroughly. like at what point it confirms buying/selling position. When to put stop loss etc.
Yes, you should open a buy trade when the market is bullish! In addition, you need to count the valid support/resistant levels to identify the validity of any specific market trend!