These are two very different types of documents. The Fourteen Points was a collection of principles that Wilson believed were essential to the establishment of a permanent peace in the wake of World War I. These principles, articulated by Wilson in a speech to Congress in January of 1918, were intended to inform the process of writing a peace treaty at the end of the war, as well as to encourage pro-peace elements within Germany itself. Its provisions included the formation of the League of Nations itself, as well as numerous statements of ideals, such as freedom of the seas, an end to secret treaties, free trade, reduction of armaments, and "fair and impartial" arbitration of territorial disputes. It also included a number of specific provisions for dividing Eastern Europe in a way that respected the nationalities of the people who actually lived in the lands in question. By and large, however, it was a statement of principles, and as it turned out a non-binding statement at that.
The Covenant of the League of Nations included a statement of many of the same principles as the Fourteen Points. But it was intended to be a charter document, one which would serve as a "constitution" of sorts for the League of Nations. So it included many provisions for the structure of the organization, as well as requirements for admission and rules that were intended to be binding. These included provisions for arbitrating disputes between member nations, the establishment of an international court, and rules for so-called "mandates," or colonial possessions of many member nations.