How to take a bullish position
To take a bullish position, you would buy the market. You can do this either by investing in the underlying market, or by trading on its price. Most investors will be bullish by default, because by investing in shares (or other assets) they own the asset outright and so rely on the market rising to realise a profit.
However, traders can also speculate that a market will increase in value with financial derivatives such as CFDs and spread bets. These products can be used to trade on the price movements of an asset without taking ownership of it, meaning they can also be used to take a bearish position.