Currently Being ModeratedJan 30, 2013 1:37 PM (in response to kekreative)
In the first place, the Firefox installer has an alias to the Applications folder in its window - you simply drag the fox icon onto that.
I'm assuming that the missing icon you're looking for is the one from the Dock?
If so, select Macintosh HD in the sidebar, find the Applications folder and drag it into the Dock (to the right of the line), being careful not to release the mouse until the other icons move aside for it. If you do that right, the Applications folder will remain in Macintosh HD, and you'll have shiny new alias to it in the Dock.