system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How exactly could a US citizen go about suing Saudi Arabia through the 9/11 Bill?
gpt
You would go to court and file a lawsuit naming the Kingdom of Saudi Arabia as the defendant.  You'd have to pay a process server to notify them, presumably through their embassy in Washington DC.  They would file motions to dismiss, noting that they are a sovereign country.  Prior to this law, the first judge that heard their motion would agree with them and toss you out of court.  With this law there could be a hearing to determine if they are immune to your suit, and to show you have standing to sue, and a zillion other motions.

Winning your case is very doubtful, but at least you got your day in court and you got to embarrass them, as much as possible.  They might settle, to avoid the legal fees, and then you'd get some money.