Where can I find the URL parameter ?

Hello,

I try to open a accordion with the URL parameter. I read the documentation about 'How to open/activate via URL parameter ?' but I cannot find where to set the url parameter.
The website I need this for is https://www.grandcafekuhlman.nl

I want to be able to open a certain accordion header when I click on a button on the homepage (for instance Pinchos Lunch ,if clicked the accordion on www.grandcafekuhlman.nl/menu opens the accordion with header Lunch). That why I need the URL parameter. Is this possible? How do I accomplish this?

Hope to hear from you soon.