Each object has decors. They are additional parts of the main objects. Decors become available for purchase after upgrading objects to certain levels (each object and decor has its own required level).
To add decor, you need to click on the object, and then add decor to the object by clicking on the plus sign. If the decor for the object is not yet available, then you will see a lock in the cell.
Also, by clicking on the beauty label you can see a window with two tabs, which describes what brings beauty to your garden:
By clicking on the plus sign, you can choose decor for the object. After adding decor, a picture with the installed decor will appear next to the object.
If you click on the decor in the window above, a window will open in which you can change the decor or remove it altogether (cross):
You can also hover over the decor directly on the coast, the cursor will change to a pencil, click on the decor and you can change or remove it.
If the decor is available to you, but you have not installed it yet, then when you hover the mouse over the place where the decor should be, you will see a plus sign that you can click on.
The decor can also be edited from the object enhancement window.