If you already have an eDirectory setup but want to install DSfW in your environment, it is recommended you utilise the existing eDirectory setup and install DSfW in a container in the existing eDirectory tree. This way you can utilise all the user information in the eDirectory container. This kind of setup is known as a name-mapped setup.
For more details on name-mapped setup, see Section 5.5.2, Installation Prerequisites for a Name-Mapped Setup and Section 4.2, Deploying DSfW in a Name-Mapped Setup