Hi Chris
The Basic 1 form that is used in the document you quote does not include a file upload control. You have two options: use a different form or modify the form.
If you change to the more complex General Purpose Data Entry Form named MNHNL Dynamic 1 and configure it, including checking the Occurrence Images box in the Species section, then you'll get a photo upload box.
Alternatively, if you edit client_helpers/prebuilt_forms/basic1.php and, within the get_form() function, insert a call to the library function data_entry_helper::file_box something like
$r .= data_entry_helper::file_box(array(
'table'=>'occurrence_image',
));
that should do the trick. Note that this is attaching an image to an occurrence but you can also attach images to samples and locations (and taxa but this would not likely feature in an online recording form) by changing the table parameter.
Look in client_helpers/data_entry_helper.php for the file_box() function to see all of the parameters that you could supply. http://code.google.com/p/indicia/wiki/FileUploadSettings is also relevant.
Regards
Jim Bacon.