First of all you need to enable either Digest or Basic authentication in IIS. Make sure you understand the security issues with each of these, specially if you are not using SSL over the internet.
In the Sharepoint website properties click "Edit" in the "Authentication and access control" section.
Enable Digest, Basic authentication or both. See my warning above about understanding the security risks.
Now go to BI Publisher and setup your Webdav directory:
In BI Publisher admin screen edit the webdav directory adding the host, port (if necessary) and match the Security setting with the selected one in the IIS configuration (basic or digest).
Save your changes.
Select the report you want to schedule and click the “Schedule” button which will display the above screen. Select “Web Folder” in the Delivery section and select your configured SharePoint WebDav directory. Enter your username/password and the path to the file you want to save. Make sure you include the name of the file (in this case I selected Price List.pdf which is the sample Price List report that comes standard with BIP). Once you click submit it will start the job.
When it’s finished it should display “Success” in the Status column like so:
Finally, go to your SharePoint site and the file should be there:
