1) Sign in to your SCA account HERE by using your email address and password.  Once logged in, if you navigate to the appropriate ticket page for the Member Presale you should be able to purchase tickets without entering your Membership Code. 
2) Member Presale tickets go live at 10AM, 48 hours prior to the public sale of tickets. Make sure you are logging in to purchase tickets after 10AM two days prior to the public sale ticket countdown clock.  
3) If you are still having trouble purchasing Member Presale tickets, try entering your Member Code on the ticket page.  To locate your code, login and click My Account, found at the top right corner. 
4) Your 10-digit membership code (6-digits & 4-letters) will be listed at the top of the page under Memberships.
5) Print or write down your 10-digit code and keep it handy for future member opportunities!