Right angle triangles: PROPOSITION 1.47; “Note that Euclid”s proposition was not about an algebraic equation a2 = b2 + c2, but about a geomtetric phenomenon involving literal squares constructed upon the three sides of a right triangle” (Dunham, 48).
Cited work: Dunham, William Journey Through Genius: The great theorems of mathematics. New York: Penguin Group. 1990
So what is seems he proposed was that assuming you have a right angle using three squares laying them upon a right angle triangle, the square areas of both along the line of points AB and the line of points AC would give you the total area of the square along the hypotenuse. With this proposition you should be able to take the illustration below and print it off at any size, label accordingly and the squares areas along the right angles should give you the total area of the squares along the hypotenuses.