How the brackets work there is no need to do angled cuts! The instructions are a little odd to me but I think with more sleep - or maybe coffe - they will make more sense. It's all pictures.
http://www.2x4basics.com/shed-kit_instructions.html
You can download the instructions in parts...look at the materials/cut list. They are pretty precise.
Which size shed did you get?
I do like that they split the cut list so if you are doing a 7x8 you're not having to weed through the other sizes.