Where to paste the AddToCalendar link in the autoresponder email?

Where in the autoresponder do you paste the link? I filled out the form on the calendar website but when it opens in calendar.google.com, it opens with Star Wars day Party?

You should follow the steps to generate the calendar link. You seem to have clicked the link from the AddToCalendar website which is just a sample.

On this form from their website:

You have to fill the fields with your preferred date, event name, location, and etc. After that, you need to click the "Update" button and copy the link.

To paste the link in the autoresponder email, simply add a new row then paste it there. Here's an example on how you should paste the link:

I hope that helps.