Category for Tasks

I guess I didnt explain that too well as I am particularly bad at that, what I was trying to do was change the attributes so I could have Task category which worked fine at the attributes page

i have attached the attributes.jpg file

but didnt show up on the task page so I could choose.

i have attached the taskpage.JPG

I altered the domain options below to include task category but am not sure how I get it to work in the task page so it would be a required field like the project and organisation. I dont know any php at all so was a bit scared of trashing it, I did go and have a look at the corresponding docs for the task module but was unsure where to add stuff to. Would you be able to post a bit of code with instructions that would allow me to insert task category on the actual page. I would also like to say that I appreciate your time and effort and your help that you have given so far.

function _stormattibute_domain_options() {
static $options;
if (!$options) {
$options = array(
'Country' => 'Country',
'Currency' => 'Currency',
'Price mode' => 'Price mode',
'Task category' => 'Task category',
'Task status' => 'Task status',
'Task status search' => 'Task status search',
'Ticket category' => 'Ticket category',
'Ticket priority' => 'Ticket priority',
'Ticket priority search' => 'Ticket priority search',
'Ticket status' => 'Ticket status',
'Ticket status search' => 'Ticket status search',
'Project category' => 'Project category',
'Project status' => 'Project status',
'Project status search' => 'Project status search',
);
}
return $options;