How do you smelt in Minecraft?

First create a working table out of 4 wooden blocks, then build a pickax,

WOOD WOOD WOOD

STICK

STICK

... then mine some stone, get 8 blocks of cobblestone and put them in your work table

STONE STONE STONE

STONE STONE

STONE STONE STONE

Then place wood in the bottom box and for example raw pork in the top and it will cook (put cobble stone in the top to make stone!)