Now that I've dragged the beach photo into the other document, I need to resize it, and I can do that easily with Photoshop's Free Transform command. With the beach photo layer selected in the Layers palette, I'm going to use the keyboard shortcut Ctrl+T (Win) / Command+T (Mac) to bring up the Free Transform box and handles around the image.
Problem is, this image is in "landscape" mode, meaning its width is longer than its height, and I've dragged it into a document containing an image that's in "portrait" mode (its height is longer than its width), so even though Photoshop has placed the Free Transform box and handles around my image, I can't see any of the corner handles because the sides of the image are extending out beyond the viewable area of the document.