Hello, welcome to dA ^___^
When I first joined this site, I found some of the features confusing. To submit art, use the drop down arrow labeled 'Submit' at the top of every page, to the right of your user name.
If you've got nothing to submit quite yet, I would recommend playing around with dA muro (submit -> draw with dA muro), which is a web-based paint application.
I'll answer any questions you have! Happy creating!