In the Production environment, Jobs are pre-generated and validated.
The user has to connect to the corresponding project in Talend Administration Center web application, which is linked to the Studio, in order to retrieve all items previously published to the Nexus artifact repository after they have been validated in the Quality Assurance environment and to execute the desired Jobs.
Once you have used the Select Job from Nexus option (recommended), you can see that the main Job properties are complete and read-only. You only need to select the context (if several), the log level to be applied and the execution server you have previously started in order to create an execution task on this Job.
Note that the selected execution server needs to have access to the project (access is defined via the Server Project Authorizations page of the web application).
For more information, see the Talend Administration Center User Guide.