Run function before import

Hi,

I need some help with custom code for WP All Import. I found this:
https://www.wpallimport.com/documentation/advanced/action-reference/
But I dont know where to put the code. Where can I call the action and where do I have to add it?

The goal is to start a function every time the import is started.
Where can I add custom code to wpallimport?
Especially for the before import function.

Thank you!

Best regards
Amer