How to insert sleeve in Chai tee

So I'm making the Chai tee and it has been going very well up until now. I cannot figure out how to insert the sleeve. I have inserted sleeves before, but this is so different I can't figure it out. I folded and it and should I only be pinning one side? Then what? It looks like from the picture after it's folded that that side is open, but mine isn't. I can only get it to work if I open it up, but then I'd have to hem it and it looks like it's suppose to be self-hemming? Is that right? I have yet to successfully finish a top. I was hoping this would be the one.... Please someone help! I looked at the sew-along, but that is no help in regards to the sleeve. I am a very visual person and just cannot figure out the next step to put it in.