questions about ARISS

I'm from korea

i just watched a reel that someone trying to connect with ISS staff as an amature,

I think it is so cool that anyone can reach out to ISS if some conditions are matched.

i want to try ... because it was my dream to be a nasa astronaut when I was a child. something is stimulated in my mind

So I have questions:

1. i heard that it's necessary to get some certification, even for amateurs. so what is it? and how to get it? where can I study?(in online) it doesn't matter if it's English. I just want to try

2. do you guys think it can be a problem as a country in war? korea has really restricted law about this kind of things ( like using unnormal wireless connection )

Anyway, is there anyone has experience with this kind of things? please give me some advice. thanks.