If you're an individual trader, you can't trade without a broker. In reality, forex trading activities are dominated by large banks around the world. Dealing directly with these major banks is nearly impossible for individual traders because they trade in large volumes. Forex brokers allow you to trade in this kind of environment by providing leverage.
Aside from that, you would need a platform to execute your trades. This is usually provided by forex brokers who are connected to trading softwares such as MetaTrader. You can install MetaTrader on your own, but you would still need to connect to a broker's server and deposit your funds in their system to start trading.
Choosing the right forex broker could prove difficult, that's why you should increase your knowledge of forex brokerages before opening an account in a certain broker.