Use the verb reestablish to describe what you do when you set something up again, or bring it back. You might try to reestablish your place as the best math student in class after a terrible midterm grade.
When something that's been there ceases to exist, you can sometimes reestablish it, or return it to its former state. Politicians constantly attempt to reestablish their party's control of government after it's been lost to the opposition, and a small child might reestablish her position at the top of the playground slide after being jostled aside. You can also spell the word this way: re-establish, which makes its pronunciation a little clearer.