1. You should have received an Account Activation email right after placing your order, to the email address associated with your account. Click the link in that email to set a password and you'll be able to login.
2. Can't find that email? Head to the Account Login page and press "Click here" under the "Having issues managing your subscriptions?" header. From there, enter the email address you used to check out and click "Get subscription login". Once you set a password, you will be able to login to your account!
3. If you have already activated your account and need to reset your password, click "Forgot password?" on the account page and you'll be able to reset it. If you do this and it doesn't recognize your email, try options 1 or 2 above.