我想在我的 Windows 2012 Server R2 上安装活动目录。我尝试使用服务器管理器进行安装。我按照以下步骤：但是当我单击“安装”时，出现以下错误：
"Installation of one or more roles, role services, or features failed.
The source files could not be found. Try installing the role, role
services, or features again in a new Add Roles and Features Wizard session,
and on the confirmation page of the wizard, click "Specify an alternate
source path" to specify a valid location of the source files that are
required for the installation. The location must be accessible by the
computer account of the destination server."
我下载了 Active Directory 轻量级目录服务 (ADLDS) 管理包和远程服务器管理工具，但仍然出现相同的错误，所以我想知道我应该使用哪些来源。我是否遗漏了其他步骤？