https://www.ibm.com/mysupport/s/question/0D50z00006LMPab/how-to-start-implementation-of-tivoli-omnibus?language=en_US
With such an open-ended question, I'm going to provide links that start at the very beginning - Event Management. IBM has a great Redbook on this topic. It's from 2004, but the foundational information is still completely valid:
http://www.redbooks.ibm.com/redbooks/pdfs/sg246094.pdf
It's a REALLY good reference, particularly chapters 1 and 2. Once you understand Event Management concepts, reasons, challenges, needs and personas, I think you then need to move on to information about the OMNIbus components, architecture and capabilities, which you can find in the product documentation here:
Then keep on reading through the rest of the product documentation so you understand how OMNIbus is basically configured.
The next topic you'll want to look at is probes. which will process data and send events to OMNIbus, and this information is also in the product documentation:
Next you'll probably want to dive into ObjectServer SQL to find out how to manage the events that probes generate:
You should probably also look at the links listed here:
https://www.ibm.com/developerworks/community/wikis/home?lang=en
Somewhere in here, you'll also need to determine if you're going to use Netcool Impact (most new customers purchase both products in some combination). And if so, you start poking around the Impact Wiki:
https://www.ibm.com/developerworks/community/wikis/home?lang=en