Are you using Construct Classic or Construct 2? If the latter, there are help forums and a search bar.
In general you will need the Mouse and Keyboard object, a "rock" with the bullet behavior, and than an action that says "When [whatever key] is pressed > spawn object (Rock); Set Angle of Motion {Rock} to player.angle"
I mean, look at the tutorials. There are lots of them. That is what they are there for.