After you have planned your answers to the questions about DNS, namespaces, files and filesystems, permissions, and passwords, which you are asked by the Active Directory Installation Wizard, the rest is just process.
dcpromo.exe can't be run by just anyone. Creating a new domain or tree requires membership in the Enterprise Administrator group, and creating a new DC in an existing domain requires membership in the Domain Admins global group. An attempt to run dcpromo by a non-Administrator simply returns an error stating that you must be a member of the Administrator group to run dcpromo.
The Enterprise Admins group exists only in the root domain of the forest. In a mixed mode domain, ...