that’s what this forum is for 
This article from our notification is a good starting point: Notifications - via Email, SMS, Ticketsystems and more
Also, this video is a good quick start: Episode 21: Setting up notifications in Checkmk - YouTube
Generally speaking, you can set up notification for anything and everything, so also for state changes on specific state changes e.g. for CPU load only.
Also, make sure that you configure your fallback email address (global settings) correctly, if not you run into this problem: Notifications based on particular sensors