What do you want:
1. A separate page If you have a a script which works stand-alone => use the wsNewpasge.php to make your own page and add it in the menu
http://wiki.leuven-template.eu/doku.php?id=en:faq:newpages
2. A link below the menu If you want to add another link in the side-area copy the last (third) one
$sideArrCoop['derde'] = array (
'name' => "Station Set Up",
'show' => 'yes',
'icon' => '',
'link' => 'http://www.desmoinesweather.org/station_setup.htm',
'alt' => $altTxt."Website van een bevriend weerstation"
);
place it just below the last one and change it as you want, example
$sideArrCoop['pollen'] = array (
'name' => "Pollen information",
'show' => 'yes',
'icon' => '',
'link' => 'http://www.pollen.com/allergy-weather-forecast.asp',
'alt' => $altTxt."Pollen information"
);
You can add as many as you like, even with an image or icon.
3. An image somewhere: If it is a small image you could add it as point 2, by setting the ‘icon’ => to the url of the image.
If it is a large complex image you could add it either as a separete page on its own or below other information, example below the AirQuality info.
===
Your original question as I understood it, was how to add a pollen warning to the air-quality script itself (http://www.desmoinesweather.org/weather27/index.php?p=15&lang=en#data-area), just like the ozone level and the other ones which are already there.
As I am not familiar with the data pollen.com supplies, I can not help you with that. As I explained in your support request, I tried to find some info on their site but as far as I know they do not supply any data at all.
And to add pollen in the same way as ozone and the others, I need a script or an API description how to get the data using an xml or scraping the page.
The data should at least contain somthing like : " pollen level for today = 1 in the range from 0 - 5" .
But without that kind of data there is not much to add.
Wim