If you do not have an account already, creating a guest account is the first step in becoming a contributer to the PBDB.
Once created, select Account Upgrade in your Account Settings to request the role of Authorizer.
If you are working under an Authorizer, they will be able to promote you to the role or Student or Enterer.
You are welcome to use the guest account without upgrade but will only be able to search and download, not edit or enter data.