ok i dont know much about cars, so go easy. I got the 5 gear auto, so when am i suppost to shift to S4 from S3?

 

It's a 4 speed auto.

If you're talking about having your gear in "S" the S4 button is simply the overdrive button.

When your speed is up and so are your revs, push the button and it'll change up into 4th.
You can also just leave the button turned on and it'll change up in 4th normally as well.