Complex sentence: Flight path is controlled by producing navigation input to the steering system (tail fins or gimbaled rocket) using angle errors produced by the antenna to hold the target near the centerline of the antenna while the antenna is held in a fixed position.
Split into simpler sentences: Flight path is controlled by producing navigation input to the steering system (tail fins or gimbaled rocket) using angle errors produced by the antenna. This steers the body of the missile to hold the target near the centerline of the antenna while the antenna is held in a fixed position.