How to make NPC's use abilities?

We worked it out on discord. Here's the code if anyone wants to try it out for themselves: I tried to add comments to explain, but comment if you have any more questions.

local effects = game.ReplicatedStorage.Effects
local NPC = script.Parent

function useFireball(playerToAttack)
    --create the fireball
    local fireBall = effects.MagicSkill:Clone()
    fireBall.Position = NPC["Right Arm"].Position
    fireBall.Parent = workspace

    --weld the fireball to the npc's hand and destroy it after .1 seconds to give the effect that it came from the npc's hand. 
    local weld = Instance.new("WeldConstraint", fireBall)
    weld.Part0 = fireBall
    weld.Part1 = NPC.RightArm
    wait(0.1)
    weld:Destroy()


    --give the fireball a velocity.
    --shooting at the direction of the player's head
    local velocity = Instance.new("BodyVelocity", fireBall)
    velocity.Velocity = CFrame.new(fireBall.Position, playerToAttack.Character.Head.Position).LookVector * 100

    --create an event that explodes the fireball when it touches a character
    fireBall.Touched:Connect(function(hit)
        local explosion = effects.Explosion:Clone()

        if hit:IsDescendantOf(NPC)or hit:FindFirstChild("ParticleEmitter") then return end

        explosion.Position = fireBall.Position
        fireBall:Destroy()
        explosion.Parent = workspace

        if hit.Parent:FindFirstChild("Humanoid") then
            hit.Parent:FindFirstChild("Humanoid"):TakeDamage(30)
        end

        wait(5)
        explosion:Destroy() 
    end)
end

while true do
    wait()
    --every 1/30th of a second,
    --loop through the list of players in game
    for i, player in pairs(game.Players:GetChildren())do
        --if that player has a character...
        if player.Character then
            --get the character's distance from the npc
            local distanceFromNPC = (NPC.Torso.Position - player.Character.UpperTorso.Position).Magnitude

            --if the player is 100 studs or closer to the npc
            if distanceFromNPC <= 100 then
                --have the npc attack the player with a fireball
                useFireball(player)
                wait(5)
            end
        end
    end
end

for some reason its not working for me please answer. I got a random npc put a script in him and copy and pasted what u said and i read the script and understoof that i need to make a folder called effects and put a fire ball inside and explosion i did that and still not working please help or anser please