To ensure images aren't cropped on mobile devices, set the image width to "100%" and the image height to "auto". Where possible, images should be no larger than 200K and JPEG or GIF should be used rather than PNG images.
1) Select the image
To select the image, click your mouse near the image then hold the mouse button down as you drag the mouse cursor over the image to select it.
Then click the green coloured 'Insert/Edit Image' button to open the image edit options.
2) Change image dimensions
In the dimensions field enter width 100% x height auto as displayed in the below screenshot. Then click 'Update'.
3) Publish your changes
Be sure to publish and review your changes.
See next