You can't. You can only have message previews and lock-screen widgets with non-secure lock-screens. If you use a secure one, like PIN, you can't get access to the quick features because, well, you chose a secure lock-screen and having those previews and widget access there would be insecure. I know, most Apple users disagree, but I actually agree with Samsung on this one... if you want a secure lock-screen, then you have to enter the right credentials in order for you to use your phone, no matter if it's only a preview.