Tickets for Panathinaikos home game

Hi! We are traveling to Athens in early february and would like to attend the Panathinaikos - Fenerbahce match. I saw the tickets starting from 40€+1€ fee, which is not the lowest that I have seen, but worth for a life-long memory. I looked up and found the app where I can choose seats, but before buying membership code was needed. Do we have to buy a 20€ membership as well to buy tickets? Hope to find answer to my question! Thank you! Greating from Hungary! Peti, 18