need to know when to start feeding my dog wet food

my dog is 2 yrs old he is 1/2 chiua and half parmaranian he is white. he only eats dry food. when should he start to eat wet food?

Anytime you want to start feeding it to him: he could have started at weaning.
   
Introduce the canned food slowly, starting with a teaspoon traded out for a half-teaspoon of his dry food (a tsp of dry is about equivalent to 2 tsp of canned). Increase by increments day by day. Too abrupt changes could give him gastric distress.
   
I personally think that half dry & half canned gives the best of both types.
   
Buy mid-level to good food, like Alpo, Iams, Purina One, Hills, that kind of level. Beneful has too many vegetables, skip that one.