Open the navigation tool (located at the top of your screen) and double click your firm. This will update your viewing to be the firm you selected. ‘Firm details’ should now be located as a left-hand menu item. Selecting this menu item will navigate you to a new page. On this page is a tab titled ‘Manage Agents’. From here click ‘Add Tax Agents.’
If your firm doesn’t appear in the navigation tool, you have not been given permission to manage your firm.