-
Click on the project level in the Building Structure and keep the left mouse button pressed.
-
Drag the cursor onto the scheme generator with the left mouse button.
A plus icon
appears on the cursor. -
Release the left mouse button.
You have added all the radiators in your project to the scheme and a boiler has automatically been added to the lowest storey of the first pipe run. The now connected radiators are marked with the symbol 
in the Building structure.