Hi
1. If you want a post container to be wide, you should set this post format to “gallery” at the right side of the edit page. If you want it to show up above all posts, you can set it sticky, go to “Posts > All posts”, just click “quick edit” link, you will find “Make this post sticky” checkbox.
2. Don’t forget to set the featured image for each portfolio posts at the bottom right of the edit page.