Hello,
In the modern Windows Explorer context menu, "Open with" no longer appears directly when you select two or more files. Microsoft simplified the right-click menu, and by design the multi-file "Open with" verb was removed from the primary list. To get it back, select your PNGs, hold down Shift and right-click (or choose "Show more options" if you see the condensed menu). That expands to the classic menu where "Open with" should be listed, letting you pick Photoshop for opening multiple files at once.