How can I populate hidden fields with Contact Form 7 Modules from a template?

Hi,

I have installed the Contact Form 7 Modules Plugin to be able to pass some values from an event (custom post type) to a registration form for that event to send the registration via email with the data for that event.

I have added the hidden fields for the name and the date of the selected event, but since I add the contact form by using the shortcode, I have no idea how to set the values of the hidden fields from within my template.

The plugin page gives only this instructions:

You can also use a filter: hook into the wpcf7_hidden_field_value filter to modify the value of the hidden field using add_filter(). If you know the ID of the input, you can also use the wpcf7_hidden_field_value_[#ID] filter.

unfortunately I’m not experienced enough to figure out how to do that or what that exactly means, so any help here would be appreciated very much!

Best regards,
Bj?rn