Here's the traditional frequently asked questions list. I'll try and add questions that are actually asked :P.
Simply click "add a question" link at the top of the page . You don't need to be logged in to add a question, but if you are not, you won't be able to edit it after it has been added, and you can't keep track of it under "My profile"
Yes, you can edit question you have added, so long as the question has not yet been answered, and you were logged in when you added it. Once a question has been answered it becomes locked in to keep things fair, so if there's something wrong with it just create another.
Any user, logged in or not, can vote on questions by clicking the thumb up, or thumb down buttons on each item. If a question drops below a net vote of -3 (for example two up votes, and five down votes) it will be removed from the content pool, and not served to users in the future. Users with the most up votes are listed on the leaderboard on the main page, so don't forget to vote for your fellow mashers!
Baby don't hurt me, don't hurt me, no more.