Specify a site URL where profile pages of your External Content Types will be created. You can update this site at any time, ...

      Specify a site URL where profile pages of your External Content Types will be created. You can update this site at any time, but we strongly recommend you create or use a dedicated site where the profile page of all your External Content Types are hosted. 

Make sure you set up the permission of the site correctly, e.g. read-and-write permission for those who need to create profile page, and read-only permission for all end users. If you need to create a new Web application, make sure you associate the Web application with this BDC Shared Service Application.