I have a combat server and want players to gain back 100 hp when they kill another person 

Hey!
Just change the health of the attacker in OnPlayerDie or any other hook, first make sure the attacker is a player also.

        private void OnEntityDeath(BasePlayer player, HitInfo info)
        {
            var initiator = info?.InitiatorPlayer;
            if (initiator == null || player.userID.IsSteamId() == false || initiator?.userID.IsSteamId() == false)
            {
                return;
            }
            
            initiator.Heal(100f);
        }

hi sorry where do i put this? 

It would have to be made into a plugin. If you’d like, I’m sure the user can send you a full plugin privately if they do not want to release it.

Sent small copy to approval