To add a question generally, type your question into the "Search
Questions, Topics, and People" bar at the top of the page, then click
on "Add Question." A dialog will appear asking for question details
and privacy settings. Once you are done filling those out, click "Add
Question" in the dialog to submit the question.
You can also add questions from a topic page. Find the bar that says
"Find or Add a Question." When you click the "Add" button from that
bar, again a dialog will appear asking for question details and
privacy settings. Click "Add Question" to submit the question.