First entry !  Download it

In the View you can see the three Axis in Colors.

Right-Click in View. Choose the Cube.

Hold your mouse left button on top left and follow the X axis to surround the Cube.

You have selected all the faces. You are in Face Mode by Default.

Right-Click in the View and choose Move/Y to put the cube on the Grid.

Move it upside till the bottom follow the line.

The Cube is on the grid.

Click [Space] on your keyboard to Deselect. Now select only the top face with your mouse

Left Button. 

Right-Click and choose Move/Y again. Move the face lower by moving your mouse to the right.

While you move, look in the Up Left corner. Left-Click when you have about 1.8

(See next image:)

Right Click to Bevel. Low it down till it stop.

Your first object is done. It's name is cube_1, but you can rename it by Right Clicking

on it. Call it Roof. (In the Outliner Window).

Click [Space] to Deselect and select all the faces like in the image.

You can now save your 3D model at File/Export . You choose the format.

Choose 3ds, it's the most recognized format of Rendering Programs.

Move the Roof in the Y axis to 0.5 and deselect it. Create a new Cube.

Click [X] on your keyboard.  You're now in Front View.

Select the Roof, like in the image. Move the Roof in the Y axis tight to the Cube by

putting the bottom line in the same place of the Cube line.

(With right click Move/Y )

If you make a mistake you can come back an action before 

with Edit\Undo or [Ctrl]+[Z] .

Click [R] on your keyboard to Reset View to the Perspective one.

Left Click in the View and Click [U] on your keyboard to Rotate the View.

Left Click in the View to stop. [R] to Reset.