I used to change kibble (I now use a totally different diet) over within a 10 day period.
Day 1 - 10% new kibble, 90% old kibble
Day 2 - 20% new kibble, 80% old kibble
Day 3 - 30% new kibble, 70% old kibble
Day 4 - 40% new kibble, 60% old kibble
Day 5 - 50% new kibble, 50% old kibble
Day 6 - 60% new kibble, 40% old kibble
Day 7 - 70% new kibble, 30% old kibble
Day 8 - 80% new kibble, 20% old kibble
Day 9 - 90% new kibble, 10% old kibble
Day 10 - 100% new kibble.
It might be worth, once you get over 60% new kibble, adding a little bit of canned food on it to make it a little more appetizing. Kudos to you for choosing a good quality kibble for the pup!