You can click edit garden under your garden, and buy stuff, and you can add items from "your stuff" page in the edit mode, and then place them where you want. You need to have points gained with a lot of different achievements
You have to buy stuff first though then you tap on My Stuff tap on one of your stuff and it’ll appear in your garden for you to move about. If you want to change the angle, return it to your inventory, or check on it if it’s a plant then tap Edit Garden and tap on the object
