Guiding Light is primarily a Blind ability that Skye must equip before casting. Upon casting she sends out a hawk. Clicking fire once sends the hawk forward in a straight line in the direction of her crosshair whilst holding fire allows her to control the direction the hawk moves by moving her crosshair in the same direction. Using Fire allows her to equip her weapons or other abilities whilst the hawk is still in the air, whereas Hold Fire forces her to keep Guiding Light equipped as long as the hawk is in the air. Skye cannot use Hold Fire afterwards if she initially sent out the hawk using Fire.
The hawk will travel until its duration expires, at which point it will self-destruct, or until Skye recasts the ability to transform the hawk into a flash that detonates after a very brief windup. Guiding Light's detonation effects work like any other flash; it blinds anything in its line of sight and can have its duration reduced by distance or the direction an affected entity is facing (see this section about flashes for more details). However, Guiding Light also has an additional effect that causes it to give off a distinct audio cue if an enemy agent is affected by the flash.
Enemies can destroy the hawk but it has its own health amount and must take enough damage for this to be depleted for it to be destroyed.