Enabling Defender WIN 8

I am new to WIN 8 & just purchased a new HP with win 8.

Everything appears except the security defaults to Norton. I do not want Norton I would like to use defender but when I click the defender icon it tells me that Defender is off & check your third party Virus app.

All I want to do is remove Norton & enable Defender.

What is the process for removing Norton & enabling Defender????