[Rectangle Mesh?]

Buying freebies again in the Marketplace, I now figured out how to add my items to my inventory.

But, when I try to put mesh to my avatar, it just shows a rectangle.

I did put my items in a folder to keep it organized, but still doesn't work.

[I bought a couple of freebies from the Marketplace. But how can I wear it in-game?]

I was buying some freebies in the Marketplace, but I can't find it in-game. Is this a problem or is there some kind of solution? I'm currently wearing a default costume. I'm new to SL so I might be asking many questions.