Wipe data and install as new

Hi everyone,

I have a Macbook pro early 2011 currently running IOS Yosemite. I am due to sell my macbook and need to wipe all data from it and install IOS Yosemite as fresh. Please could someone guide me on the steps that need to be taken.

Apologies if there is already a thread with this information. Unfortunately my searching skills haven’t found any.

Thanks!