This is what the shirt used to look like (I started to cut it up and then realized I hadn't taken a picture of it yet, so I put it back together for this shot ha)
Here are the different pieces I cut the shirt into. I had to unpick the little pleats that were on the front of the shirt. I sewed the two large pieces together on one side.
I and wound my bobbin with elastic thread.
The finished product on my darling model.
Sorry I didn't take more step by step pictures. I was trying to hurry and get it done while she was sleeping. Please let me know if you have any questions!