When did louis come to power and how did he rule

I'm going to assume you mean the most famous Louis -- that is Louis XIV of France.

Louis XIV came to the throne as king in 1643, at the age of 4, when his father, Louis XIII, died.   While he was a child, his mother, Anne of Austria, served as regent, and Cardinal Mazarin was chief advisor who ran most of the government.  Louis XIV began to rule on his own beginning in 1661, after the death of Mazarin.  He remained on the throne as king in France until his own death in 1715.

Louis XIV was known as the Sun King because all activity in France basically revolved around him.  So much so was that the case, that members of the nobility competed with each other for the right to help the king get dressed in the morning!  It was one of Louis XIV's goals to keep the ranking nobles from being a threat to his power, so he lured them to come live at the glorious Versailles palace with him. That way he could keep them under his influence and away from their lands in the provinces.  They were lavishly entertained, but lost the real power they would have had as lords governing in their provincial lands.

Louis XIV also subscribed to the idea of the "divine right of kings." That belief was summed up succinctly by Bishop Jacques-Bénigne Bossuet, who was court preacher at the royal court of Louis XIV.  Bossuet said that monarchy "is sacred, it is paternal, it is absolute … the royal throne is not that of a man but the throne of God himself."  The claim of kings' divine right meant their authority could not be challenged because they were put in their office by God and were to be respected as God's sovereign representatives.