Just type it into the big "Ask on Pandora Hearts Answers" box at the top on any page and press the ask button or hit enter.
Clicking on Ask creates a new article with the title being your question.
Then you can click on "Answer Question" if you want to answer your own question.
Make sure your question is about Pandora Hearts or something releated to it, like anime,manga,DVDs or books.
If you accidentally add a misspelled question, you can rephrase it.
See Wikianswers:How can I get my question on Wikianswers answered more quickly? for advice on getting answers.