Hi, moving your mouse to the top right corner of your X-plane window doesn't make the settings button appear?? This is very strange.
It's a shame to reinstall X-plane just for that. It's usually never required.
You should first delete your X-plane 11\Output\preferences folder and launch X-plane, see if it solves the problem.
But if you really want do reinstall X-plane, you just need to delete X-plane folder and download one more time the installer :
http://www.x-plane.com/kb/digital-download-install/
Then, follow the steps and enter your product key when requested.
The digital download and the DVD set are two independant products, so I doubt you can receive the DVDs unless you purchase them. But I'm not part of Laminar Research team so I might be wrong about that.