Where to go to turn Plant fibers into silk?

Does anyone know how i can get silk, or how i can turn plant fibers into silk?

What is linen used for?

You can't craft plant fibers into silk- only linen. Linen is a rare crafting material that is used for several armor sets, much like Silk is. As far as I know, the only way to get silk is via salvaging it from items, however. I've never seen an NPC that could craft silk out of anything.