Before we start with image editing, let's learn to manage graphic files. First of all, open a few pictures using the following ways.

§ 1. Pull down "File > Open" to display the "Open" dialog box* that is pretty much a standard system file box with a preview area at the bottom. Another nice feature is the Favorites button in the upper right corner. Add our sample folder to your favorites; chances that you will use it often. Then select one or more image files (hold down [Ctrl] key while selecting multiple items) and click "Open".
*Alternatively, you may call this dialog by double-clicking in an empty area or using [Ctrl + O] keyboard shortcut.

§ 2. Select a recently opened image in "File > Open Recent" menu.

§ 3. Pill down "File > Browse" to launch the "Bridge" (image browser), find an image on your computer and double-click its thumbnail.

§ 4. If you open multiple files, they open in separate document windows. Please note that only one - active - document can be edited at any given moment. Before editing an image make sure to select appropriate document window.

§ 5. At the bottom of the "Open" dialog, press "Use Adobe Dialog" button to switch to an alternative view. The Adobe dialog offers some additional sorting, organizing, and navigating options.