Help with startup script in container

First off this forum is weird. Is it only pertaining to dockerhub or can I ask other questions?!?!?

I need to know where the best starting point is. I am trying to create a splunk install container that I can use in my CICD for sanity checking my configs. I am able to build up the machine and then commit it as a image, but when I start the container splunk is not running?!?! I would like to be able to have a bunch of things run at start time, how do I do this? As of right not the splunk image in docker hub run sensible at startup and I would love to learn how to do that, but the documentation is lacking clarity (for me at least).

Any help is MUCH appreciated!