Hi Escobar, at the back of your stereo set you will also have a connection for your aerial if you want to listen to the radio.
There will be two wires for your speakers.
There will also be an Earth wire, I think they are always yellow/green wires. Just connect that to any screw that you can find that is screwed into the metal of your car
There is also a Positive wire which is usually "Red" Take that wire through a hole into the engine compartment, if you can find one, and attach it to one of the connectors that hold your fuses in place.
Better still, pull out any wire from the back of your ignition, connect the Positive wire to it and push it back into the ignition. This way the stereo will stop working when you turn off your key. If you leave your car with the stereo on, your battery will go flat.
Thats' how I installed my stereo and it works perfectly. Just remember R4's don't like heavy rock music, keep it gentle!