To get to your den, click the Den Button located at the bottom right corner of your screen:
To furnish your den, click on the Edit Den button next to the globe:
This will bring up your den item inventory. Remember, land den items can only be seen and placed in land dens, and ocean den items can only be seen and placed in ocean dens.
Next, click on the item you want to put in your den. Too see all of your den items, use the blue arrows on each side of your inventory. Once an item has been placed in your den, you can move it by clicking the item and dragging it with your mouse. The screen will follow where you want to go. When you have the item exactly where you want it, let go of the mouse button. You can rotate items by hovering over the item and clicking on the yellow arrow next to the item. If you decide that you don’t want that item in your den, just click on the blue X to remove it and send it back into your inventory.
You can do lots of other fun things from the Edit Den menu such as organize your furniture and wallpaper, recycle items, switch dens, and shop.