To soften a square face use a deeper shade of either powder or blush and apply to the edges of your jaw line. Apply blusher across the cheekbones.
To shorten a longer face or soften a pronounced chin, brush the chin with a natural but deep shade of blush.
Round faces need additional contour to add shape. Blush is a must on the cheeks and deeper shades applied to the jaw line to help recede it. Emphasise the chin using a pale brush dotted onto it.
More tips:
Foundation | Concealer | Powder | Blusher | Your Face Shape