I have an idea and design of a craft and want to build it, but do not know where to start, how to design it or even what software to use, though I know its excellent idea.
I'd be tempted not to try using any software
reach for a trusty 2H and a 12" ruler
then just draw it on paper (it's been done like that for 100s of years) you should feel reasonably comfortable with it -
as long as the dimentions are right (ish) then build a mockup (balsa is easy to work with)
I know how you feel with the weather we've been having.
Refer to the Bible (old testament) I think you'll need Gopher Wood & you'll need to find the modern day conversion measurement of a Cubit.