Put camera behind player.

; Transform a point behind and above the player, in player space, to global space.
TFormPoint 0, 5, -5, Player, 0

; Position the camera at this global location.
PositionEntity Camera, TFormedX(), TFormedY(), TFormedZ()

; Point the camera at the player.
PointEntity Camera, Player

; And if you don't want the camera to pitch down...
RotateEntity Camera, 0, EntityYaw(Camera), 0


Do this each frame.