… start a discussion: Just click the button on the left, choose the appropriate tag(s), give the discussion a meaningful title, and type away. If you cannot find an appropriate tag, file it under Off-topic and request the desired tag under Technical Support if you wish.
… format a post: You can format your posts with Markdown. If you are not familiar with it, you can find a quick overview here. Do not fret – it is really easy to learn. And you will see a formatted preview when replying to a discussion; unfortunately this is not yet available when starting a discussion.
… attach a file: This is not possible for the moment. If you feel the urgent need to be able to do it, let me know and I will make it happen.
… get email notifications: By default email notifications are only activated for discussions you are following. Find your Settings by clicking on your name in the menu header bar. Here you can (de)activate certain notifications and choose to automatically follow discussions you replied to.