How to make script begin working when Player is a value?

So uhhh i need help. i don't know how WaitforChild() works and wait() is not working for me here's code i guess

wait(10)

for i, v in pairs(game.Teams["Civilian"]:GetPlayers()) do

v.Backpack.Fireball:Destroy()

end

(Don't mind if you copy it [and i think i'm asking too much today])