A deadlift is a really important exercise which forms the foundations for many more exercises, but it is also often done incorrectly. This exercise works a whole host of muscles including the hip extensors, glutes, quads and core.
Take your feet just wider than hip width apart, bend the knees and grab the bar with your arms just wider than shoulder width apart. Before lifting the bar up off the floor, ensure that your bum is low, shoulders are pulled back and the core is engaged. It should feel like you are creating tension with the bar and would be ready to lift it at any instant. From here you can stand up, bringing your hips forwards and shoulders back. At the top of the movement squeeze into the core and the glutes.
At the bottom of the movement you should be looking at the floor and then when you reach the top of the movement you should be looking straight ahead.
You may find it helpful to check your own form by setting up a camera or finding a conveniently placed mirror to ensure that you are doing the movement correctly.