if you actually carry on a business of share trading & wish to report your tax that way, you fill out the Business & Professional Items (which is the 3rd section of the old Tax Pack booklets & forms) :
i became a 'Business' for the 2009 year because i got hammered in the GFC and would have had a large CGT tax bill for 2008 if I did not change from CGT to a business (i amended my 2007 tax return from CGT to a business)