New disk on MacBook, how can I install OS X
First get your hand on a USB drive 4Gb or more
Next download and install this program for windows : http://www.acutesystems.com/scrtm.htm (15 days trial), it will allow you to format and create a bootable usb installer for mac easily.
Open the program as an administrator, insert your usb drive, right click on the drive and choose Format the disk for mac, it will take a couple minutes to complete the process, and then right click again and Restore with Disk Image and choose a DMG file,you may get a warning just click YES.
Now Insert your usb into your mac and install the OS.


If you have trouble finding ta DMG of the OS X you prefer, you can download Yosemite from here : http://getintopc.com/softwares/operating-systems/mac-os-x-yosemite-free-download/

(This is not an official link, if you're not sure about the validity of this file and don't want to download this. I suggest finding another machine running OS X, or install it on your machine and from your new OS create another USB bootable device following this method https://support.apple.com/en-us/HT201372 and redo a fresh install)