Windows Media Services (as install pack) is not inculed in Windows Server 2008 R2. If you want to install first you have to download an .msu file.
Here you can find the file: http://www.microsoft.com/en-us/download/details.aspx?id=20424
Before you start the installation of the Media Services, install the Desktop Experience Feature and its dependencies.
The .msu file will install the Role to you Server. After this you have to open the Server Manager and have to choose the Streaming Media Services Role with its dependencies.
On Windows it means a simple next, next, finish and restart procedure. Following the restart the Streaming Media Services Role will be installed on your computer and it will be found among the Administrative Tools.
You have got two possibilites to open the administrative surface.
1. Use the Management Console
2. Use the Web-based Surface (For this you have to choose this opportunity during the installation.)