The campsite is listed through Matkaparkki.com, a service for booking overnight stops for motorhomes and campervans. Sites can be searched on a map by date and required facilities.
Bookings are made in the app or on the website after registering with an email address. Payment is by card, and the confirmation includes arrival instructions. Sites are run by independent operators. The entrance here is wheelchair accessible.
Stayed overnight in a campervan or motorhome? Describe the arrangements in the comments for future travellers.