help recording a song

everything seems to be working fine. I import, or load my mp3 set up the Mic. But when I hit record and start singing the voice starts recording at the end of the music. Every youtube video I watch when they hit record the voice track is right under the music, and lined up where my vocals start recording at the end of the song what am I doing wrong?

Hold down the Shift key when you click the Record button (or “Shift + R”).

We don’t currently recommend YouTube tutorials for Audacity as virtually all of them are out of date, or inaccurate, or misleading, or just plain wrong.
The Audacity manual is up to date:

Have you tried going to Edit->Preferences->Recording?
The “Other Tracks While Recording” checkbox should be checked.
Also the “Always Record on a New Track” should be checked.

That should get you recording over the backing track (overdub).