The first event that lead to the Civil War was Dred Scotts case. His owner John Emerson brought him to a free state but the supreme court claims that people of African ancestry are not citizens. This separates the north and south because the north fears that slavery will spread more while the south thinks they can spread slavery.
Later John Brown raids the Harpers ferry to take weapons and give them to slaves to help them escape and cause riot. He gets caught and is executed. Then the south fears more rebellions.
The election of 1860 was between Lincoln, Douglas, Breckinridge, and Bell. Lincoln ends up winning.
After Lincoln won southern states decide to leave the US because they are worried about Lincolns views on slavery and what he will do
Those southern states form a new Union called the confederate states of America. Which has its own rules and rights.
Lincoln wants to avoid war because he doesn't want to be blamed so he sends recourses to fort Sumter. But the confederacy attacks it. The civil war begins.