In the FirstPersonProjectile blueprint, click the ProjectileComponent and in the properties window add a 'OnProjectileBounce' event handler.

Copy the pictured nodes.

You can now check that when hit, a projectile will give damage (but not much else will happen yet).

In the FirstPersonCharacter blueprint, add a float variable named 'Health.' Set its default/starting value to 100. (You must compile the blueprint first).

Right click the event graph and create an 'AnyDamage' event handler.

Copy the pictured nodes.

Finally, in the Project Collision settings, create a new Preset named DeadChar, with the pictured setup.

You should be able to kill NPCs and your character with projectiles now.