Add Option to Admin

Hi,

How can I add an option to the Admin > Settings Page, I know how to create a whole new admin page using add_menu_page, but I only have one option to add so I would like to add it to the already exisiting General Setings page. Is there a function for this or is this even possible?

Because i’d rather not create a whole new admin page just having one option on but I may have to take this route!

Thanks ??