Your dog is a PUPPY. Learning to stay out of stuff takes time, and in the mean time, you have GOT to prevent him from having access to stuff you don't want chewed. This means a crate, an exercise pen, or doing a REALLY good job of puppy-proofing your house and removing everything you don't want chewed from his reach, and correcting him (verbally) as soon as he STARTS to pick up or get into something you don't want him to mess with.
In the mean time? Get a crate.
In the mean time? Get a crate.