This can be used in two ways.
It can be mainly a listening exercise. The students listen to the teacher describe what is in the space 'There is a bear sleeping on the sofa' and they draw in that detail. After adding the 10 details they can then write sentences about their room.
Alternately they can make pairs with other students and create the details themselves. Either play rock scissors paper and the loser tells the winner a detail they can add to the space. Or be cooperative and share details. In the later case I'd have student A say a detail and both add it then student B say a detail and both add it. This is the way I use the worksheet. To introduce the target language on the board I draw 'a cat sleeping in a box', 'a rabbit jumping on a chair' and 'two birds playing badminton under a table'. Then starting with the cat I ask 'What is this?' 'What is it doing?' and 'Where is it?' then I put them all together as a single sentence 'There is a cat sleeping in the box'. I have the students then make the next two sentences 'There is a rabbit jumping on the chair' and 'There are two birds playing badminton under the table' before demonstrating the game with the JTE.
Once they've added 10 details they can write sentences about the space.
An additional activity could be naming things. After adding ten details they can name the things. For example 'there is a bear sleeping on the sofa' is followed up with 'The bear sleeping on the sofa is Henry'.
The pictures used for the room worksheet were taken from a worksheet posted here. I can't remember where it is now though.
After this activity I usually use 'park life' as a follow up activity. I add names to the pictures I drew on the board to demonstrate 'park life'