I'am only 16 years of age do I suppose to use that whitening cream? And were I can buy it?

I assume you are asking about tooth whitening.

I don't use the stuff, I just brush 2-3 times a day and floss at least once a day. Tooth whitener can cause sensitive teeth. So before you go as far to use the stuff, I would make sure you are taking care of your teeth properly through brushing and flossing.