Your Store account and your program portal (library) account are separate accounts (although they are linked together in the background by email address).
When you make a purchase for the first time in the store you will need to create an account (Register) and be sure that you use the same email address you use to login to your program portal (library) if applicable. Register HERE
After you set-up your Store account and complete your purchases, your programs will be added to your program portal (library).
Going forward, you can login to your Store account to see your purchase history and checkout faster.
NOTE: You are not required to set-up a Store account (although it is recommended), the purchased programs will be added to the account associated with the email address given during checkout.
If you have already set up a Store Account you can reset your password by clicking, "Forgot Your Password?" Reset your password HERE
If you are a new purchaser with no previous programs you will receive an email with instructions on how to access your programs within your program portal (library).
See the Help Center article HERE