Go to Settings > System & updates > System navigation > More, and enable Navigation dock.

After the Navigation dock button appears, you can:

• Drag the button to your desired position.

• Touch the button to go back.

• Double-touch the button to go back two steps.

• Touch and hold the button, then release it to go back to the home screen.

• Touch and hold the button, then swipe left or right to view recent tasks.