how do you apply mindfulness in everyday life?

Being mindful in everyday life can be done by practicing mindfulness in daily activities.
This includes brushing your teeth mindfully, mindful eating, even mindful walking.

The main point is to just be aware of yourself throughout the day, and of your surroundings.
This is not an easy task, and can easily be forgotten and lost from our focus throughout the day. A great way to improve this is to choose daily activities to be mindful during, such as brushing your teeth.

The way you would go about being mindful during these activities is by focusing on what you are doing. If you are brushing your teeth, focus on each tooth being brushed and the motion of your hand and the brush, and how it feels and tastes.
If you are mindful walking, notice how each step vibrates in your body, notice when your heel hits the ground and how that make you feel. Notice the sound your heel makes when it hits the ground. Notice what you are stepping on.

Being mindful in daily tasks and daily activities is a great way to train yourself to be more mindful in everyday life, while reducing the potential for losing focus from mindfulness. This is because instead of just trying to be mindful all day, you are choosing specific times and activities to be mindful during.

You can start with one or just a few activities per day, and slowly you should see that it becomes easier and easier to stay focused and mindful, and you will naturally be able to apply this practice to other tasks and activities.