I shall give you a mini-tutorial
So up at the top you have the deviantart logo, which will take you back to the site home page, where popular/recently submitted art is displayed. You can favorite art that you like and watch artists that you like
And if you want to submit art you click submit and it'll take you through the process. If you click on your own username it will take you to your page, where you can set up a gallery, write a journal entry, etc etc
And then there's a little message icon that will take you to your inbox, where you receive deviantWatch messages (from artists that you watch or groups that you've joined) and feedback messages-- when somebody comments, or favorites one of your deviations (deviations are submitted pieces)