You can start right away with positive food treats for incentive. Keep the sessions short since he's a little guy. 1-3 minutes 3 times a day in short sessions. Teach sit and down and spin and then with a clicker and treats in hand while he's still having fun see what you accidently capture like roll over dead, or sit like a slop. All these little cute accidents you can capture and click and treat and use later for a great dead-bang dog or put all 4 paws in a box etc. The younger he learns to learn the more he will learn and the more fun it will be.
I posted the science behind clicker today that was very interesting. Take a looksee.