Some system templates will resize images for you on upload. But others, with very precise layouts, require specific sizes that cannot be done by the system programatically. These images need to be cropped manually. Each image upload field will have a tooltip 
that tells you the exact size (in pixels) that is required for the template. The pixel perfect resize and crop required for this is best done separately with a dedicated tool. There are many free solutions out there – we recommend a free online tool called Be Funky.
To access the Be Funky image editor click here
To watch a short video that shows you how to use Be Funky click here