Alliance?

Press the Scroll button on the bottom right hand side of the screen, then click Send Messenger. Choose the shield of the kingdom you want to send a message to, and when the screen comes up with the message, choose "Offer Alliance". Don't worry about the stuff typed in on the bottom, you can say whatever you want and it's still taken as an offer for alliance. If they accept, they'll send your messenger back with an approval message and you'll be allied. This is especially good to have early on in the game if you can ally with those between you and enemy countries, as you most times don't have to even fight them. Hope this helps!