It looks different because it is a different tool, but it is not more difficult. In order to create a link to an uploaded file in an assignment description all you need to do is to select some text and then open the link editor. From the link editor you can browse to your course Files folder and select the file you want, much the same as in the resource. If the file is not in your course files, you can upload via the link editor and then link to it. You do not have to leave the Assignment settings page for it and you do not have to copy and paste any URL.