When you first install SharePoint and open Central Administration for the first time, you’ll be given two choices, either to run the configuration wizard and let SharePoint do the administrative tasks for you, or configure the farm yourself.
If you configure the farm yourself and decided to add the Managed Metadata Service, you would simply go to Application Management>> Manage Service Applications>> Click new and choose managed metadata service. The SharePoint will create the Service Application for you. So if you try to click on the Managed Metadata Service Application you will be presented with the following error:
The Managed Metadata Service or Connection is currently not available. The Application Pool or Managed Metadata Web Service may not have been started. Please Contact your Administrator.
To Solve this issue, go to Central Administration >> System Settings Tab>> Manage Services on server>> and notice the managed metadata web service, its not started by default. click start and go back to your service applications page and view your service application. Note you may need to wait fora minute so that the error will disappear and you can use the service application.