The AE tracker works on a layer view not a comp view. That is what you get when you double click the footage.
You then go back to the comp, select your target, like a null, and apply the tracking info to that null. You can't add a null to the layer window.
Just go back to the comp to work on the comp. The layer window is only for looking at and working with that single layer. You can not work on anything but that layer in there.
There are dozens of motion tracking video tutorials out there. Most are ok. I'd take a look at a few.
Here's a whole workshop on motion tracking:
If you don't have a Lynda.com membership, you can start a free trial membership that'll last plenty long enough to watch that 98-minute series.
Rick, when I go back into the comp tab after tracking in the layer view, I am no longer able to pick a source to apply the tracker data to. I can only apply it to whatever is in the layer tab, for instance if I create a null layer in there it will let me choose it as a target... So do I do that then copy the null from there to the comp view windows? Otherwise, I really cant go back to the comp layer to work on it. Confusing. I will check more motion tracker tutorials though i have watched a few in the past and have successfully done motion tracking on some projects before, I just dont understand why this one is seemingly giving me hassle.
If you have a null in your comp and you track your footage, then when you are in the tracker, with the footage layer selected, you can edit your target and apply the tracking info to the target. It has always been that way and it is explained in every tutorial I have ever seen on the use of the tracker.