How to add a whole package to transport request by code?

My task is to do all these steps programmatically:

• Create a new transport request, I managed to do this with TR_INSERT_REQUEST_WITH_TASKS
• Add package content to the newly created transport, this is the part I am stuck in.
• Release the transport, I managed to do this with TR_RELEASE_REQUEST

My problem is that I can manually add the package to the transport request via transaction SE03 and then release it with FM TR_RELEASE_REQUEST, but that is not the goal, everything from step 1 to 3 has to happen in one program execution if anyone can guide me how to do step 2 it would be very helpful, thanks in advance.