I need some serious help guys, someone died and I'm in over my head

First of all, I can provide details if you want. I know this is kind of vague at the moment, and for that I apologize.

As I stated in a previous post, I am still "new" to the game. I really am figuring it out as I go. As I've seen recommended on here, I started trying to unify Ireland. I've done that, and was slowly creeping into Scotland to try to make an Empire. I was doing okay. . . heck, Norway declared war on me for Argyll (Norway's been wrecking shit in the UK all game). Well, I knew that I was married to the Princess of England, no big deal. Suddenly, in the middle of my war with Norway over "Skottland," I get a notice that I can call in an ally. . . the Kingdom of Jerusalem. What the shit? The King (of England, her father) died, and I guess the man in charge of Jerusalem did, too. Oh, there's KoJ's county in the middle of Skottland. Okay. WHOA I am now the King of Ireland, Wales, and Jerusalem. What the hell? I prevailed in the war against Norway/Sweden (yay!).

Then my wife called me to war against a Muslim country near Jerusalem (I can't even tell you who or which, because I got interrupted in checking. . .). So I'm raising my levies. . . again. . . and get interrupted by this... The emperor, who had been a distant relative last time I checked. . . died

I don't know what to do. Now Ireland/Wales/.5Skottland are in the Byzantine Empire, of which I am Emperor, as well as Jerusalem is under my watch, the Golden Horde has been wrecking shit to the East (I've seen the notices!) and I have all kinds of Duchies I can usurp and I don't even know where to begin to corrale all this in...

Any tips on how to approach this inheritance would be greatly appreciated. Me and my family have always been doing backyard politik in the UK. . . we don't know how to handle an Empire.

All the best,

Emperor Lugaid nac Briann

Emperor of Byzantine Empire or something

King of Ireland

King of Wales

King of Jerusalem too, fuck it why not