To resize an image you’ll need to drag the corners of the white boxes around the image. You’ll start by selecting the layer on the left side, or clicking on the image. Once the image is selected, you’ll see a white square box appear on every corner of your image, and you’ll see a thin black box outlining your image.
Hover your mouse over one of the white boxes, then click, an arrow will appear. Continue to click and then drag your mouse diagonally in the direction you would like to go.
For more download the video tutorial below: