[How do I change shape/skins?I'm stuck with default textures]

I'm really new, just joined yesterday!

I got the hang of rezzing my items, so I'm not clicking on them and wearing a box. It shows up in Edit Outfit but my avatar is still the same as default? I can only put on clothes and hair. I got Iffy Shape ~*By Snow*~ for example, clicked on it, and it changes my shape but the skin is still the same (but the item in the shop seems like it comes with a skin?). The same happens with an eyepack I got

Putting on other skins/makeup does nothing and I really dont want to be stuck with an ugly default face :(

EDIT: and how would I fix clothes if they clip into my body?