To access Interactive Questions, you will want to be on the Video Management Page for the video you wish to create interactive questions for. You can do this by simply opening the video you wish to add questions to from your My Videos Page. From there, you will see a button labeled 'Interactive Questions' under 'Video Features'. Clicking on this button will then open the Interactive Question page.
To go back to the Video Management Page for that video, simply click on the video title in the upper left hand corner.