Please add a two boxes instead of category. first one main category and secound one subcatogory like cascanding. and i dont know how to remove the tiltle box and make title category. I try so hard but its not working i dont know what should i do, please help me

Try this function:
<?php ItemForm::category_multiple_selects(null, osc_item_category_id(), __('Select a category', 'epsilon')); ?>