Your account will be the e-mail address you put down for the username and the password is the word password, which you can change. Please allow up to 24 hours for the account to be created .. sometimes sooner. Accounts are manually created so try your username/password within 24 hours of buying the membership.
If you are already a member and you upgraded to personal weatherman then your account was already upgraded and when a Q and A session is called you will be able to access that section while logged into the website