In order for the host CICS region to recognize a COBOL system running on a local client, you need to define a connection definition and an associated session on the host. On most host systems, a CICS region change such as this is usually applied by the system administrator. Liaise with your system administrator to perform this process.
You need to have a resource group for the connection and session definitions. The example group value is HSTTOSNA. The example connection name is LU21 and the session name is LU21SESS.
You can use an SNA Server 3270 applet to configure the host CICS system by entering the VTAM ID of your host CICS region when the terminal has a connection to the host VTAM system.