How does the United Nations work?

it doesn't

The United Nations focused on preventing conflict.

The United Nations started shortly after World War 2, so their main goal was to prevent more world wars. They protect human rights as well as turning peace into conflict. To do this, their work is carried out in many ways - by courts, tribunals, multilateral treaties - and by the Security Council, which can approve peacekeeping missions, impose sanctions, or authorize the use of force when there is a threat to international peace and security, if it deems this necessary.