Need help! - having car trouble with my phantom car alarm

[Sponger15SB]

So, I bought a used car 2 months ago, a Toyota Camry LE.

From what I know, the car did not come with an alarm system, and there was no clicker that came with the keys, it was just a normal key.

Last month a friend and I were at the store, and I get into my car and try to start it, and an "my" car alarm started going off and the engine wouldn't start.

I was incredibly confused, and had no idea how to turn it off. So we fiddle with it for what seemed like 15 minutes and somehow we got it to started.

Now, I went out to my car the other day and I cannot get it to start because the alarm keeps going off again.

Any suggestions as to how to get this [censored] thing to shut the [censored] up so I can start up my car and take it over to a mechanic so he can get this to never happen again.