Under Connection Type, you will see the Access list. Defining a JDBC or OBDC connection typically requires all of the remaining fields associated with the General tab to have the correct information. If you are into abstracting those details from your metadata domain, then use the JNDI method of access.
The JNDI access method keeps your server implementation cleaner as well; once you publish your domain to the server, as long as you have defined the JNDI connections with the same names, you still have a good implementation where your database information is only described to the JNDI layer. To take advantage of the JNDI method of access in the Pentaho Metadata Editor, you must define your database connection information in a properties file for the editor.