Sounds like you need 4+ animation frames...
crosshairs-not locked
crosshairs-locked (highlighted, bolded, or brighter color)
The missile
Smoke / flame (for the thrust)
What perspective do you want the animation?
What do the crosshairs look like, both locked & unlocked
What type of missile?
Describe the timing and steps of the animation.
What type of graphics style? (realistic, RTP, cell-shaded(cartoon),...)
For the missile & crosshairs, google "missile" & "crosshairs", select "images" at the top, and choose 1 or several example images
I'll move this to Resource Requests for you.
Be Well