How to spawn a missile entity which can fly to the target coordinate

[sdddddf80]

How to spawn a missile entity which can fly to the target coordinate？I try to use the function like new EntityMissileIncendiary(world,x,y,z,a,b). It's supposed to be spawned at the coordinate (x,y,z) and fly to the target coordinate (a,b). But it just stays at the coordinate(x,y,z).