You need to update it’s velocity.
Eg this will apply a = 20 m/s /s on world Z axis which will result in a > g (which is 9.8) and will make the projectile fly above instead of falling to gravity.
To control this with keyboard, you need to create an event that will update velocity according to your needs (how much, in what direction, etc) on your projectile and call it when input is received (when spawning projectile, store its reference at your pawn and in pawn keyboard event call event on the projectile).