OpenCV - Face recognition - where do i put images?

Hi guys!
I am very new to OpenCV but eager to learn! Been doing Home Assistant for a couple of years now.
I have installed OpenCV on my RPI and i want to make a face detection automation for my home.

My question:
Could anyone please give me an explanation on how you get the pictures you need in the xml files?

Do you have a link inside the xml file or is it decoded or something? i am also wondering what kind of xml editor you are using.

Hope you have time to answer, tnx in advance!

Emil