Shut your eyes; think back to your childhood. Can you remember the house of a friend or a relative that had a different smell from your house? Let your mind wander over it; let the place come to you.
When you are ready, write down as much as you can remember of the different smells, for example, food, perfume, clothes, tobacco, people, pets, etc. But pay particular attention to all the concrete detail, all the ‘things’. Look your notes over and, using them, write a page recreating this place. Do not worry about creating character or telling a story, let this emerge through the things and place you describe. Concentrate on using smell but get something in from all the other senses too.