I gave https://www.google.com/search?q=How+to+Optimize+WordPress+Website+Speed&ie=utf-8&oe=utf-8 a quick read so my question to you is why you can't use that research first?
It's not a new question so here's the awful thought that crossed my mind. We are seeing spammers that ask an oft asked question to shill for a product later. Let's hear what you think.
How to Optimize WordPress Website Speed?