To crop a portrait, go to the page the portraits appear on, select the grid and click the Crop tool in the contextual menu.
Click the Crop button in the bottom left corner of the portrait to be cropped.
Use the handles to adjust the size of the portrait.
Use the Move tool (cardinal arrows) to click and drag the portrait into the desired position within the frame.
Once the portrait is positioned correctly, click anywhere on the page outside the portrait grid to exit crop mode.