MadyNora: Simply just drag two items on each other in the inventory.
Sometimes you need to drag items into a forge, or a grindstone etc.
kmja: so its only trail and error???? becase when i have read a book i get a new recipe its only the same text as the book i did read
the book usually says something like "Using my knife on animal hides tured them ito something useful"
So knife+hide.
But trial-error works as well. I found many recipes by trying to stack items. For example I treid to stack wool, and I ended up making something else instead :)
Or sometimes you must think: without any spoilers, there is a quest wehere you must kill something, and lure it out at the same time. So think with crafting: a lure + something that kills = perfect bait.