I got my One Plus One smartphone today. I also ordered
OnePlus Tempered Glass Screen Protector with my Sandstone Black 64 GB phone. Unlike other screen protectors, which leave air bubbles, this was a breeze to fix. I got this right first time. Just I watched an amazing video showing the easy method.
Before the video, below are some images to show how I fixed it.

Video on How to apply the screen protector on One Plus One:
https://www.youtube.com/v/Jr00DfyTsR4