Well, the scripts are just text files. The game will load all .cs files in the various script directories, there is no other requirement - they just have to be in the right folder and the game will attempt to use them.

If you wanted the events to be part of the unique realm campaign, then you would modify Data\Scripts\Campaigns\Iron Barony\IronBarony1.cs for the iron barony.

If you want them to be available in all games where the player is playing these realms (or even when the AI is playing them - Galeni's Recognition and Aevinwode's Choice work in this way), then you would want to creat a new script for each one in Data\scripts\Campaigns\Plugins

If you go the plugins route, you alos need to modify CorePlugin.cs. This plugin basically loads all of the other campaign plugins (to avoid every campaign having to reference them all) - the only change there is to add your plugin to the list.

I can't say much more without knowing which route you intend to go down. I would suggest that you look at Data\Scripts\Campaigns\Plugins\AevinwodesChoice.cs - this is a campaign plugin which creates an event very much like what you are describing here - Aevinwode must decide if they want to ally with Sirucil or with Sonneneve. There is also a _Template.cs in that folder, which contains the bare minimum required for a plugin to not crash - as it's name suggests, it is intended to be copied as a starting point to save a little time.

Keep in mind, I'm not using the Beta, so maybe that's part of the problem. But there is no Campaigns\Iron Barony folder. Should there be or do I need to create one? Also, there is no plugins folder, so I'm a little confused.

Should I join the beta to get access to these things?

Well, the systems for modding are very different in the beta - I would advise joining if if you want to create mods, so that you don't end up having to create them multiple times in different systems.