If you don't have it set-up already, log in to your Google Calendar (online). On the left hand side, under Other calendars, click 'Add' > 'Browse Interesting Calendars'. Then, click on the 3rd tab 'More' and you should see the 'Contacts' birthdays and events' calendar, click 'Subscribe'. It should then add your contacts birthdays to your google calendar.
On your EVO, go to the Calendar, click Menu > More > Calendars, and check the Contacts' birthdays and events calendar to view it on your EVO Calendar. (You may need to sync with Google before you see your new calendar.)