Inside a function or any where add below code :
add_user_meta(‘userid ”new_field_name’,’value’);
eg:
add_user_meta(‘1’, ‘bonus_points’,’1′);
Getting value from this field:
$user_current_points = get_user_meta(‘1’, ‘bonus_points’,’true’);
updating field:
update_user_meta(‘1’, ‘bonus_points’,’20’);