After login on the portal Citroën service and Peugeot Service Box follow these steps :

1. change the language (if you didn't change it befor login) in the right upper part "Mon Profil" and put the required language
2. in the top menu select Free services » Spare parts
3. left upper enter your car identifier(VIN number) or select your vehicle model
4. Select the main group your spare part may occur in
5. put the group more precisely
6. new row appears under grafical section (e.g.: 0230 06 617501A FRONT BUMPER ), click on it
7. you should see the desired spare part now

In the case of you didn't found the right spare part, close the popup window and in the bottom section select another group, or return back by clicking on the red triangel (two red triangels: return top - Vehicle general).