[Entering Embedded Document A.Designer]

Working on a sample image with Affinity Designer I placed a photo on the worksheet.  After resizing and moving the image around I wanted to enter the embedded image as shown in the tutorial for using the refine selection tool.  One is supposed to be able to “double tap” the image and enter the image to then change persona “Pixel” to do the refine tool.  But I cannot double tap the image to enter it.  What am I doing wrong??  Is there another way to enter the image, change persona and use the refine tool and not affect the entire sheet??  Using IPad Pro and latest version of Affinity Designer.