Perhaps your difficulty comes down to not knowing the history of Christianity so well. For example, did you realise that throughout the history of Christianity, there have been conflicts over the meaning of Scripture writings? Hence there has been a history of discussion, debate, study by theologians and scholars within Christianity. Eventually for Christian unity an authentic interpretation has been made in each case where essentials of belief are at stake. These are recorded and preserved as part of the deposit of faith. You can find documents and doctrinal statements by knowing which issue you want clarified. For example, if you want to know the scriptural genesis for the doctrine of Original Sin, the Church has those records preserved and at this stage of history, they can be easily accessed in libraries all over the world.
There isn't a verse in scripture that states 'Original Sin' in doctrine form, but there are collections of verses that together show the way to that conclusion. Can you understand how it works in the light of that? You can't just scroll through a list and find a verse that states the doctrine of Original sin, which seems to be what you are expecting should happen.