How do I install OS X back after replacing it with Windows 8

So I got a MacBook Air recently and I installed Windows 8 onto it, only windows, nothing else. I did write the Mountain Lion image to a USB first just in case I wanted OS X back.

So now I want OS X back in case there are firmware updates. I plug in the usb, hold option and then power it up, choose Mac. The apple logo shows up, with the loading thing under it, after a while it becomes a circle with a slash, still has the spinning loading thing, doesn't seem like anything happens.

Am I missing something? How can I install OS X back on my MBA?

Reset the PRAM and try again. See the following LINK.

I'm still getting the slashed circle.

If you're still getting the circle with the slash after resetting the PRAM, that indicates your USB flash drive with the ML image on it is not bootable.

Is there a way for me to make a bootable OS X Mountain Lion USB now that I'm using only Windows?

If this is a new machine, released with Mountain Lion, then you will need to use Internet Recovery. This is done by booting in recovery mode.

Turn the machine on, press and hold Command + R. Continue holding and it should boot from the EFI, prompt you to connect to WiFi and eventually allow you to download OS X and install.

You'll likely break Windows 8 in the process, however, so backup before you do so.

It came with Lion, free Mountain Lion upgrade through Apple.
I'm assuming this will still work but I just get Lion again right?
Should I hold Command+R before hitting the power button?
Also, any cloning software you recommend?

Sekito said:

It came with Lion, free Mountain Lion upgrade through Apple.
I'm assuming this will still work but I just get Lion again right?

Click to expand...

Yes.

Should I hold Command+R before hitting the power button?

Click to expand...

No, start with the machine turned off. Turn it on and immediately press and hold Command+R.

Also, any cloning software you recommend?

Click to expand...

For Mac - CarbonCopyCloner or SuperDuper!
For Windows (on a Mac) - WinClone.
For Windows (on a normal PC) - Acronis True Image

I decided to just wipe windows without backing it up and just have os x on my mba. Thank you all for helping me.