How to put songs into the iPhone 5?

Okay so I need some help doing this, before I used to just drag and drop the songs I wanted to add to my Iphone/iPod to the iTunes library and then sync them, but while I was trying to do that today some songs wouldn't add to the iTunes library and some did I checked to see what was the matter and I couldn't find anything. If anyone knows how or another way I can do this pliz help I would gladly appreciate it.

Download the app called free mp3 music downloader ( it's free ) and click Browser and go to the address www.mp3skull.com, search the song that you want and click "Download" and then, it will start downloading the song, it usually takes about 5 to10, seconds to download email me at chinesepersongofer@gmail.com if you still need help