How do you keep it from sitting on your head?

Hello! There are velcro straps on the inside that are adjustable, similar to a backpack. Once they are adjusted to your needs, the costume will sit properly and not hot your head. Thanks and happy shopping!

How do the straps attach? I put them around my shoulders but where do they attach? To each other at the ends or somewhere on the inside of the box?

Hello, The costume comes with instructions to assemble. Inside the box costume there are velcro straps. There are similar to a back pack. When you connect the inside straps, you can adjust them to your best suited needs for comfort. Thank you and happy shopping!

How does the strap inside the box work? I assume it's to hold the box up so that it isn't sitting on your head?

Hello! There are straps inside the Box costume to secure to your shoulders as if you were wearing a back pack. Once the box is assembled, you will see the velcro straps inside when you place the costume on your body. You can accommodate the straps to fit your needs and comfort. Thank you and happy shopping!