How do pins work?

So a few questions.

My gf and I will go to a Disney park for the first time this December, and I saw that there is a lot of community around the pins on social media, but to be fair, I'm pretty lost when it comes to how to get them, where, and when, how to trade...

And also, I saw on the website that the 13th some pins of Rapunzel are getting dropped, and she's my gf's favorite princess, so I would love to get her both, but I'm so lost I don't even know where to start. You must make a queue online? Or just for the special ones? There will be any pin when we arrive on the 15? How can I get them? Any help would be amazing.

And if you drop any recommendations for the first visit, it would also be really appreciated. I want this trip to be one we don't forget. Thank you for reading 🥰