Local Customization of Repository

I am a Computer Science student and as part of my thesis, I am supposed to modify the creation, update, and deletion of EMR in OpenMRS. I would like to ask for help on how to access and what repositories I should use to do these modifications. I am only supposed to run these modifications locally and for the specifics of my thesis. Your assistance would be very much appreciated. I hope for your response soon. Thank you.

Did you get a chance to look at this? https://devmanual.openmrs.org/