I was wondering how to use matinee.
I hava checked the document but it only includes a lot of theories.So I cant quite understand it.
Also,I download the official demos Matinee.What I found is that it is also beyond me.
So can anybody help me ?
youtube is your best answer 
just check it it have a lot of great simple tutorial .
It requires a subscription to the site, but I remember this course being pretty good for a quick practical introduction:
http://www.digitaltutors.com/tutorial/1919-Introduction-to-Matinee-in-Unreal-Engine-4
yeah digital tutors worth every penny , but for a beginners you don’t need to put money to get it as its free in youtube .