Lupita, I have seen plans for these projects at some speciality hard ware stores. Sunset Books has a paperback full of children's projects along with plans, material lists, cutting lists, and estimate of money outlays.
I would check this out first.
But if you do not have any luck here, I would build a deck the size of the house, build your walls, cut out your windows and doors, lay your rafters, apply your siding and roof decking, paint and shingle.
What you will be doing is building a rough in scaled down version of a square actual home.
Lupita, if you do not find the plans in the books that I suggested, come back on the site and we can walk you through this project.