How to download my mp3s to my new iPhone 4s?

I just got a new iPhone 4s. All the music I have is in the form of mp3s that I downloaded off youtube videos. How do I get these on my iPhone?

IPhone supports mp3 music well. You just need to drag and drop the music into iTunes library, connect your iPhone to computer, iTunes will detect the iPhone automatically, then click iTunes menu "File -> Sync iPhone", the songs will be transferred from iTunes to iPhone.

If you want to know how to convert video and put DVD movie on iPhone, I think this step by step guide would help you.

You can import them to your iPhone 4S through your iTunes.