Only the administrator can view a hidden poll. If you are a Doodle account user and are currently logged into your account, the results of your hidden poll will automatically be shown to you. Simply open your poll from your dashboard. If you created the hidden poll without a Doodle account, you need to click on the admin link in the email you got after creating the poll. If you lost the admin link, you can have the email resent here.
A hidden poll can be opened up to the participants. Open a poll using the admin link. Click on "Edit" then click on "Settings" in the Wizard navigation. Uncheck the hidden setting.