WordPress doesn’t make this easy, but when you go to your Media Library and click on the “Edit” link for an image, in the upper right is a box labeled as Save. The “File URL” field has a link in it…this is the one you would use for the path to the image. Likewise, if you do a fresh upload of a new image, click on the “edit” link next to it after it uploads to get to that window to grab that url.