Stack Overflow gets new design. How can we get such design to our site? Is that some that our mods need to import or it will be done by SO Team or do we need to request for such designs?
New design and theme is now Live.
If you mean the "left navigation bar" by design, See Live: Left nav, new theming and responsiveness
You can check or uncheck the left navigation bar by going to your user preferences and check "Hide Left Navigation". THe options will move to a drop down menu after doing that.
There will be no change in the theme and design as long as the site is in beta. There will be just default "white and blue" design. New changes in the design only applies when the site graduates. Designers from the Stack Overflow will post an update on our meta site and ask for opinions about our own theme when that happens.