Click on any photo in the layout preview window to enable the scale and move options. If there is a text layer in front of the photo try again in a different area that does not conflict with the text bounding box.
Us the slider to scale the image up or down. You can also select a different image filter to change the way the image looks.
Click on the image again and click and drag to reposition it. Alternate scaling and moving actions until you finalize the correct position and size for the image.