You can use heat to soften the material of your new shoes. Using a blow dryer, blast your shoes with air (make sure to move the blow dryer around to evenly distribute the air and avoid melting the material). Once the material is warmed up and more pliable, gently twist and bend the shoes in the center to break them in. Don't go overboard and bend them so far that they don't return to their natural shape, or so hard that they break.
Consider a lower or more comfortable style. Choose a thicker and more stable heel like a platform, wedge, or chunky heel to provide more support and weight distribution. Shy away from pointed-toe styles if you have wide feet or toes, opting for round or almond-shaped instead. You can also buy heeled boots or heels with ankle straps to help support your ankles.