You can also enable the feature using an Administrative command prompt, useful for keeping a script around to easily add features needed on the fly.
For example here is how to enable Telnet:
Code:
dism /online /Enable-Feature /FeatureName:TelnetClient
Deployment Image Servicing and Management tool
Version: 6.3.9600.16384
Image Version: 6.3.9600.16384
Enabling feature(s)
[==========================100.0%==========================]
The operation completed successfully.
To see the names of features to be able to script others, issue the "dism /online /get-features" command.