Hi guys I bought the item Moonlit Moss Covered Rock and I can not put the Avatar in it. Is that so?

You have to make sure that your "Base" layer in your wardrobe is listed above the background.

And how do I do that?

On the left side of the wardrobe, you'll see a list of everything you're wearing and then some other layers for your Base, eyes, mouth, etc. You can drag and drop those layers in the order you want them to show on your HA. So just take the Base layer and drag it above the layer for the backdrop item.

Be sure to click the "wear" button once you have your outfit how you want it to look.

I'll try. thanks