I could be level 3 or 4 in Aimed Shot, but need level 1 before I can get Level 2? Any ideas?  Where did u acquire it in Darnassus as a mission?  I must have dropped it from my list or when I added all therse extra bars I misplaced it somehow? where can I find it again?

in your spellbook...

Level 1 Aimed Shot is gained from speccing it in your marksman talent tree. Once you've specced it, you can train further ranks. If it's just the icon then wowullah's right and it will be in your spellbook! And you can't "lose it" unless you respec.

Like he said above, it's the 11pt talent in the Marks tree.  If you are specd for it you will have it automatically.  If not not spec'd at least 11 into marks to get it your out of luck.