I don't see a button to cause a reopen vote.
You need 58 more rep (3000) to do that :-)
See your privileges list: https://ux.stackexchange.com/privileges/close-questions
OK, so since this Rahul's answer isn't going to make sense once my rep changes.
For anyone else coming along later the answer seems to be:
You need a rep of 3000 (or more) to do this.