Arriving by plane you should take the special bus to The Main Bus Station. Then take the bus number 1 and go to the next-to-last station: restaurant 'Karlo'.
Once you are off the bus, it is 1 minute walk to the apartment. Proceed walking by the main car road and take the second street right which goes uphill a little bit. The first building from your left is yours, and the first entrance door you see from the left is the door to the apartment.
There is also a very cheap taxi service in Pula: Taxi Cameo 060700700