Put the sun in the lens. The flare is built from a light source you place: a bright core with a long-tailed halo, glare that lifts the frame around it, spikes from the aperture blades, and ghosts across the center.
Placement
Put Flare X and Flare Y over the brightest point already in the shot, such as the sun, a lamp, or a window. A flare anchored to a real source reads as optics; one floating over a shadow looks pasted on.
Intensity, halo, and spikes
Intensity and Halo Size set the glow. Starburst Spikes sets the number of diffraction spikes, from none to 12. The flare is fixed, so it works best on tripod shots, slow pans away from a steady source, and title backgrounds.