If you go to the top left of the window click edit> preferences> addons search for "import images as planes" and enable that addon, then you should be able to drag them in from your file browser. Or you can add a plane go to the shader editor drag the image in there, and then plug that into the surface slot of the material output.
you can enable wireframe view by selecting it in the top right of the 3d viewport window, from the selection window by pressing "z". you can enter edit mode by pressing "tab"