I know this post is old but I still want to let you know it is possible: you want to go to "manage your trip" without being logged into your account (https://booking.evaair.com/flyeva/ev...spx?lang=en-us) then on the left side of the page you should see "input membership card no." and here you can manually input your account number, and this will enable you to add that flight to your account.