Messaging - can't link contacts or chat

I'm unable to get started using Messaging. I don't recall if when I set up Messaging it gave me the option of linking contacts to Messaging, or to do this when I set up the computer but if so perhaps I did it incorrectly. When I open Messaging it says I am connected to Messenger. When I click on 'add an account' it lists Facebook but gives no other options. At the moment I only want to chat with one of my email contacts; I have a Hotmail account. I have tried the 'invite' option but it keeps saying 'this page is temporarily unavailable'. I'm sure this is supposed to be simple but I don't get it; would be grateful for your help. Thank you.