Q: Install OS X on my macbook pro, i only have windows installed

Hello everybody

First time here on the discussion board, I have a MacBook pro 13", I think it's mid 2012, my hard drive suddenly got corrupted and it was no longer usable, I replaced with a new one, I used bootcamp assistant on my brother's MacBook to make a bootable usb for windows, since the new hard drive has nothing installed on it. when I installing I pressed the option key on startup and selected EFI boot after windows 8.1 installed I realized that a lot of the features weren't working like editing files on external drive and no audio at all, bootcamp driver installation would not complete successfully, and from time to time the computer crashes with a bsod, after a deep research on how to fix those issues mainly the audio one, I realized that I should have installed using BCA and not EFI since apple does not support EFI.

I have 2 important questions.

1) How do I install mac OS X back on my laptop.

2) how do I boot from usb with BCA since pressing the option key displays only EFI, and not pressing anything directly takes me to the malfunctioning windows.

Thanks in advance

P.S. I would appreciate if you give me quick replies since I need my laptop to do some work.