A shopify free theme named"Brooklyn"it will be nice if you can tell how to stretch the image to full size,thx

Could you kindly tell me how?

Hi guysI am new and wondering how to add images right under the product descrption?like thisI am now using the free theme from shopify, and I tried to add image in the  descrption, but the image that I added is always on the right, I couldnt make it ...