It's often useful to grab an image's file location for re-use in HTML elsewhere throughout your site - for example, in a text widget in your sidebar. Here's how to do it.
1) Open media library and mouse over desired image.
2) Click "Edit" to open the image resource in edit mode.
3) Double-click in the File URL field and copy this string. You can now paste this into HTML code somewhere else. [note: the image resource can be closed without saving.]