Submitting an assignment in Moodle is as simple as dragging and dropping. This feature in Moodle works best in Firefox and Chrome, but Internet Explorer has mixed results so please try a different browser if you have any issues.
You can also access instructions in the 'Getting Started as a Student Online' resource. This appears in the Moodle Student Support Forum option, from within every Moodle shell.
It is recommended that you don't leave submitting your assignment to the last minute, just in case there are any problems with technology. You can contact the ITS Service Desk for assistance with issues.