When you're working on your draft, please be sure to click the Save and Continue button on the bottom of each page. If it doesn't automatically move you to the next tab, it means that something on the page is not correct or complete, and you'll have to update information on the page before you can save your content again.
Be sure to check that the "start date" of your campaign is either the current date or in the future.
***IMPORTANT: If you click on the tabs at the top without first saving you work, you will lose the data.