PO Boxes, how does it work?

Hi,

I’ve been trying to figure out how PO Boxes here work. I’ve registered and paid on this website: https://eposta.posta.sk/pobox/

Now according to google’s translation, the courier will post a letter somewhere (?) for me to pick up my package on my PO Box.

I am still so confused. Few questions below:

1. Where will the courier post the letter?
2. When I order online, do I enter the given PO Box number and PO Box zip code as my address and not my home address?

Thank you.