You can [Answer your own question](http://superuser.com/help/self-answer):

> **Can I answer my own question?**
> 
> Yes! Stack Exchange has always explicitly encouraged users to answer
> their own questions. If you have a question that you already know the
> answer to, and you would like to document that knowledge in public so
> that others (including yourself) can find it later, it's perfectly
> okay to ask and answer your own question on a Stack Exchange site.
> 
> To encourage people to do this, there is a checkbox at the bottom of
> the page every time you ask a question. If you have more than 15
> reputation and already know the answer, click the checkbox that says
> "Answer your own question" at the bottom of the Ask Question page.
> Type in your answer, then submit both question and answer together.
> 
> Alternatively, you may go back and add an answer to your own question
> at any time.
> 
> You can also accept your own answer, but you must wait 48 hours to do
> so. After all, someone else may come along with an even better
> solution to your problem!