Thank you so much,

You have to enter creative mode. When you press the button with a + sign, it will open the mode for building figures. Once you have finished your figure, save it and press the wrench icon at the top. This will load the figure into the diorama, and you will be able to use it.

Please, how do you create a diorama? I can't find it in the game in the creation section, I created figurines but I can't place them,