I clicked on the mac icon at the corner left at the bottom of the screen. I would choose download, desktop picture, etc but now I clicked on the mac icon but I only saw the mac and Bob's. What do I do?
Your Downloads folder, your Pictures folder, etc. are all inside your home folder. Your home folder is inside the Users folder, which is the last folder on the right bottom of your window (the one with the little person on it). You can quickly go to your home folder from the Finder's View menu, or type Cmd-shift-H.
Make Finder active, then go to the top menu, and click Finder, then Preferences. Make sure you have the Favorites checked that you want to view in each Finder window. (from the Sidebar tab at the top)
I couldn't find the desk download folder from the mac icon but I clicked at top of the screen and I saw the desktop and download folder. How do I copy the folders and put them inside the mac icon?
They don't belong inside the Mac icon. They belong in your home folder. It sounds like you are new to Mac. Perhaps you should make an appointment at an Apple store to have someone show you around.
Ah, well, that's another reason that I have for not liking Gallery view, so far. I have not used Gallery view much, and I try it now and then, but always go back to "comfortable for me" List view, and the ever-useful (for me) sidebar.