1. You can't name your function the same as an existing MTA function, otherwise you override it. Rename your function to something else.
2. You need to put your command in quotations, as it's a string. The way you have it now as just createFire, it's looking for a variable called createFire, no variable of that name exists so it's returning nil.
3. Use proper indentation! Else should be in line with if, outputChatBox should be on a seperate line.
4. You realize that on line 5, it's going to check if the player element is == "admin" (Hint: it won't be)
5. You're using local incorrectly... In fact, line 1, 2, and 7 as far as I can see are useless.
6. You're creating a fire at 0,0,0? Uh, why are you getting player position then?
Here's I guess what you meant to do.
function fireAtPlayer(player)
if (true) then --replace with an admin check, use getElementData/setElementData after they login to verify they are admin? Or use ACL to check their permissions
local x,y,z = getElementPosition(playeR)
createFire(x,y,z,1.
else
outputChatBox("You're not an admin",player)
end
end