How to override Spree checkout process Or How to Remove any state during checkout like "Delivery" state? Spree Ecpmmerece

How to override Spree checkout process Or How to Remove any state during
checkout like "Delivery" state? Spree Ecpmmerece

I'm using spree 2.0.0 in my application. I just want to know how i can
edit spree chekout or how i can completely remove/disable any "State"
during Spree checkout process.
Any thoughts on this.
Thanks.