The IMS jobs, etc. used to configure the IMS system on your image can be found in data set IMS1210.INSTALIB (the HLQ is based on the IMS level you have installed). What you will have to do is to locate the stage 1 macros in your INSTALIB data set and add your new transaction to the stage 1 source. BTW a modblks gen should be sufficient to add a new transaction. Submit the JCL to assemble the Stage 1 and this should generate the stage 2 jobs. Submit them in order (the will need to be released since TYPERUN=HOLD is on the job card.) Once the Stage 2 job have completed successfully, you will need to submit the online change utility to copy the new modules that define your transaction, the corresonding ACB members and your new map from the staging data sets to the data sets referenced in the JCL control region JCL. Generally I copy all data sets (MODBLKS, FORMAT, ACBLIB, etc) to both the A and B concurrenlty while IMS is down and then do a cold start to bring IMS back up. If you would like samples of these jobs please contact me offline (emitchj@gmail.com) and I will provide my jobs.
MitchJ