You don't specify what method you're using to add the clip, nor what specifically happens when you try, but the simplest is probably just to drag the clip down to the sequence. If it won't place on the track you want, drag it below the available tracks and a new one will be created for the clip.
OK Here it is:
1) I imported clips that were shot wih a DSLR CAMERA. I Double clicked on one of the clips to load it into the Source Window, I set my In and Out Points and I dragged it down to the New Item icon and a new sequence with the clips settings was created. Then I added a few more clips to it (Video only) (All shot with DSLR) and it went down fine. Then I imported a song, it's a AIFF File 48,000 khz and 16bit. I loaded that into the Source window and set my In and Out Points on it. (I also noticed that when I brought the song into the Source window, The V on the left side of the timeline went away like it should because there is an Audio only clip in the Source window. So I added the Music clip to A1, by using a keyboard short, after the last video clip. This is what I wanted. No Problem.
Here comes the problem.
2) I imported footage that was shot on Mini DV and captured by FInal Cut Pro (they are Quicktime Files) into the Premire Browser. I then doubled clicked on one of those clips,and it went into the Source Window like it should have. I set an In and Out Point and then I dragged that clip to the New Item Icon and a Sequence opened up with the setting from that clip. All is well so far. I added a few more clips to that timeline without a problem. Then I double clicked on my song (The same one) to load that into the Source window and set my In and Out Points on that. HERES THE PROBLEM. I noticed that as soon as I loaded the song into the Source Window, both the V and A1 buttons on the left of the timeline dissapeared. This should not have happened. Only the V one should have dissapeared, not the A1 button. Becuase of this I cannot add the Audio to the timeline anywhere? I tried dragging it onto the timeline, but all I can see is the playhead on the timeline move to right, like it did add it, but it did not. I did the same thing with the keyboard shortcut and the same exact thing happened.
Why can't I add my song to the timeline with footage that was shot on Mini-DV?
Thanks in advanced
I tried dragging it onto the timeline, but all I can see is the playhead on the timeline move to right
That's somewhat contradictory. The playhead won't move when you drag clips down, only when you Insert or Overlay. So if you saw the playhead move, that tells me you haven't dragged the clip down with the mouse.
Try adding an additional stereo track to your sequence and trying again.
That happens automatically when you drag the clip to an empty space below the current tracks.