With the game alone, you can’t truly become the High King in Skyrim. In theory, Dragonborn, the main character, has great power but it simply does not suit the High King position. While some in the gaming community wish that becoming the High King was a feature, others argue that it doesn’t make sense, in terms of lore, and in terms of Dragonborn’s habit of leaving for quests, for him to become High King. However, there is a Nexus mod that allows you to become High King. The High King mod includes a unique quest to become the king. Do keep in mind that this mod was released in 2017 and the mods you always download at your own risk.