How to add a DC (Domain Controler) to an existing domain ? -

1. Run dcpromo.
2. On the Domain Controller Type page, select the Additional
domain controller for an existing domain checkbox.
3. On the Network Credentials page, type the user name,
password, and user domain.
4. On the Database and Log Folders page, type the location in
which you want to install the database and log folders, or click
Browse.
5. On the Shared System Volume page, type the location in which
you want to install the SYSVOL folder, or click Browse.
6. On the Directory Services Restore Mode Administrator
Password page, type and confirm the Directory Services
Restore Mode password and click Next.
7. Review the Summary page, and then click Next.
8. When prompted, restart the computer.