Editing images is almost the same as editing text. Just click the image, then hit the pen tool. A menu will pull out on the left-hand side of the screen. To change the image, click the replace image button and select your desired picture from your computer's files.
If you want to change the size of a photo, hover back over it on your webpage. Then, use the zoom slider to choose your desired size.
Be wary, that you can now stretch the image beyond its original dimensions, so it's important to ensure it doesn't pixelate.
To adjust the height of your photo, hover over the bottom of your image until a black arrow appears. Then, slide this up and down as needed. This arrow will snap to images and text to keep your webpage neat.
If you need to crop your image, left-click on any part of the image, then drag your image to your desired position.
You can also adjust the Width, Height and Alignment from the sidebar under Size.