Importing A Blueprint
Importing a blueprint is optional, but it does make drawing your house easier.
You can create your own blueprint using a paper, pen/pencil and ruler and then take a photo of it and import it into Sweet Home 3d, or you can search the internet for a floor plan similar to the house you want to design, and even if your house was for sale once, you may be able to access a floor plan of it already that you can take a photo of and import, or download from the internet.
There are many options for a blue print, and It only needs to be good enough to allow you to roughly gauge the positioning of your walls and layout.
Once you have an image you want to use for your blueprint, open Sweet Home 3d, and go to the menu option, Plan->Import Background Image and then select your file.
You then have an option to set the scale of your image. You need to drag the ruler start and end points to a place on your image where you know the real measurements of it. In my video, I know the wall length that I moved the ruler to is 1300 cm.
You then need to set an origin point on your diagram where you want 0,0 to be. I usually use the top left point of my blueprint image.
I have also added the floor plan blueprint from my video if you would like to use this in place of your own.