Trouble adding Layers into the default Blank Ai file

I used the "blank" Ai file and replaced things to create my first puppet, and I can't seem to add layers under the "head" or  "body" portion. Essentially I can't make any new layers, or drag them into, the original framework. I'm trying to make more hand positions and I can't place them within "body", it just shows a lock icon. Why is this? I've included an image of the layers I have in case this helps but otherwise it's hard to demonstrate.