Contact Form 7 Dynamic Text Extension custom field

Hello,

I jus installed the Contact Form 7 Dynamic Text Extension plugin, however, but I’ve got some problems with it.

Visitors enter a page with a list of trainings. Every training has a button that leads to a page with a form (contactform7). It would be nice to insert automatically the training name in the form they have clicked on.

In the backend of contactform7 I chose a Dynamic Text field.
In the field: Dynamic value (optional) I wrote: CF7_get_custom_field key = ‘my_custom_field’

My question: What should I enter in my training(shortcode?and where?) page so the dynamic text field knows which word it has to fill in the field?

Thanks in advance,
paul