At the Athens - Patra National Road (E65), if you are coming from Athens, after the 150th klm, you will see the exit to Akrata. (If you are coming from Patra the exit is after SEA Akratas.)
At the end of the exit you will turn right to Aigeira (there are sings to help you).
After 2-3 kilometers you will see on your left hand a bank (National Bank of Greece - Εθνική Τράπεζα της Ελλάδος).

At the second road (Kratinou - Κρατινού) you will turn right and then left.
 
Outside Blue Ark Aigeira Flat & Studio are 5 little trees and then there is your parking space.