LED light strips come in all sorts of variates. So when you say:-
I have a strip of LED RGB lights that i want to use
You need to say what sort of strip do you have and provide a link to the data sheet of it, otherwise no one can give you solid advice.
You can get LED strips that need a complex control signal squirting in them allowing you to individually control each LED in the string. Or you can have strings where all the red LEDs are controlled with one signal, the same for green and blue.
If you have this sort of string then you need three of the circuits in that link and then you feed them with PWM signals from the arduino.