Example: To make a Web Header for our event manager use the tool below:
Upload your image then switch Auto to Manual
Type in the aspect ratio 140:39. The number might adjust slightly, but the image will remain the right ratio. Move around your image cropping till your happy with it.
Once you like your cropping, you can scale your image by clicking the
button and type in a specific size (2800x780px for Web Headers) like this.