Sometimes even simple things are not totally obvious.  Administrators for your term store have the ability to add and modify new term sets, configure settings and security, and manage your individual terms. 

If you are in your Term Store Tool you may notice that your user actually doesn't have access to the term store.  The tell tail sign is that the user you are logged in as is not an administrator or term store owner that allows contributions.  Notice that Administrator does not have access but SPAdmin does. If you look at the Managed Metadata Service in the tree you will see that there is NO drop down to managed the store. 

If you user has access you will be shown the options to modify the term store.  Notice the small drop down arrow to the right of the Managed Metadata Service in the tree.

Add your user to the Term Store Administrators if you need access.