Olive oil mix in dog food, how much and how many times should i mix it a day?

i heard that some people mix olive oil in their dogs food but i don't know how often you do that? i've got a bichon and papillon mix, 1 1/2 yrs old and she shed a lot after winter, (don't shed winter). i've got an answer last month that maybe because it is spring thats why and one said put/mix olive oil in her food, but i really don't know how much (tbsp/tsp) should i mix. And if you just do that a day or twice a day?