How do I make it where you have to reload?

Greetings, it depends on how you have your scripts set up and how you have the ammo set-up.
One way for example is to have a number value set in global properties (for a player). In your shooting script, have it check if the number value is above zero, and if so, to fire a shot and subtract ammo from the number value.
EX (you will have to adjust to fit your specific script)
if global.property["ammoinmagazine"] > 0 then //checks if there is ammo in the magazine
//insert whatever stuff happens when you fire the weapon here
global.property["ammoinmagazine"] -= 1; //subtracts one bullet from the magazine
end;

Building from that:
if global.property["ammoinmagazine"] > 0 then //checks if there is ammo in the magazine
//insert whatever stuff happens when you fire the weapon here
global.property["ammoinmagazine"] -= 1; //subtracts one bullet from the magazine
elseif global.property["ammoinmagazine"] == 0 then //only applies if you are out of ammo
print("out of ammo!");
//you can also add more code to say, display a message that you are out of ammo
end;

Further building from that:
if global.property["ammoinmagazine"] > 0 then //checks if there is ammo in the magazine
//insert whatever stuff happens when you fire the weapon here
global.property["ammoinmagazine"] -= 1; //subtracts one bullet from the magazine
elseif global.property["ammoinmagazine"] == 0 then //only applies if you are out of ammo
print("got to reload!");
wait(3); //waits 3 seconds to simulate reload time
global.property["ammoinmagazine"] = 30; //puts 30 bullets in the magazine
end;

You can further expand the code to meet your needs, but I hope this gives a good starting point.

That is up to you. I highly recommend you read through the documentation and some of the tutorials to get an idea of you can do within the engine. For example you could play an animation when firing, or have the lighting change, or play a sound. (And you can do all of the above at the same time!)