<p>When a closed question is edited by the asker (as opposed to someone else just fixing it up), it is automatically entered into the 'reopen review queue'.  No flagging is necessary.</p>

<p>If it is edited by someone else, it will need to be either flagged (a mod will review the flag), a reopen vote cast by yourself (for those who have 3k rep), or a reopen vote cast by someone else (consider going into chat to ask if anyone can start the ball rolling).</p>

<p>The details of these mechanics are in the MSO answer to <a href="http://meta.stackexchange.com/questions/186722/can-we-have-the-ability-to-flag-for-reopening/186728#186728">Can we have the ability to flag for reopening?</a></p>

<blockquote>
  <p><strong>Adding items to the queue in response to 3rd-party edits.</strong> Currently, this is done when <a href="http://meta.stackexchange.com/questions/157584/should-questions-be-added-to-the-reopen-queue-as-soon-as-theyre-edited-by-the-o">the author edits</a>, but not if <a href="http://meta.stackexchange.com/questions/157584/should-questions-be-added-to-the-reopen-queue-as-soon-as-theyre-edited-by-the-o">someone else does the same</a>. It would be possible to change that - although there are <a href="http://meta.stackexchange.com/questions/183233/give-2k-users-a-dont-put-this-in-the-reopen-queue-checkbox?lq=1">some pitfalls</a> we'd have to avoid. </p>
</blockquote>