pins 1.Emitter 2.Base 3.collector
Do as follows.
Step 1. Find gnd (0v) on the battery terminal, connect 0v to 0v on your circuit (so both grounds are linked)
Step 2. Middle pin of your transistor, base, well, connect a 300/1k/etc.. ohm resistor (Depending on the signal, you may have to increase/decrease the resistor value) to an Arduino Pin Digital 2 for example.
Step 3. Take the 2 Wires, Place 1 Wire on the Collector of your 3 pin Transistor.
Step 4. The Remaining 1 Wire, place that on the Emitter
Step 5. The Tricky Part - if you don't have a voltage meter, if you do, find out which of the 2 pins is + and - connect your meter up if it reads -3v reverse it, then you'll have it reading 3V/Red black/0v (gnd) (-/gnd pin goes to your emitter, the other + pin goes on your collector.)
Step 6, connect the 0v side of the transistor (emitter pin) to Gnd of your circuit (or NOTHING will happen)
now when voltage is applied to the base of your transistor, it create a short across your emitter and collector (edited, i typed base?) (which is the same as you pressing the button on the remote control, with only using 10000th of the energy) since a button is a "short" i expect some kind of resistor which measures the button press, if not, you may have to do something like place a resistor in series with the emitter/collector with either negative or positive rail..
unless I missed something out, that should work, once you've done it you'll see how simple it is (only takes 40 seconds to do once you've done it) - you can use a similar circuit to invert a signal to check out
This is all off of memory so I may be wrong and you may have to place 0v on the emitter (not either like i thought) and + on collector, the diode does not allow it to flow or does it? now i'm confused, but i know this method works fine as I use it to turn my computer on and off via bluetooth (there's a long wire running inside my PC to where the power switch is, and now it's connected to a digital pin on the arduino, i can fire up the pc or turn it off via hardware with a touch of a button from my phone)
it's also a lot cheaper and good to learn :)