Website running slow

Hi guys,
My website https://www.themostcrazy.com Its slow and I have know php or html knowledge ?? i did a yslow test its telling me that I should ADD EXPIRE HEADERS. I dont know how to do that. I have installed wp super chache. In google page speed it has added another thing that I should optimize images. I already installed Smush it plugin. I think that my wordpress theme load all the image full and shows them small, thats why it take much data to load. So any suggestion