by Something that helped me a ton to gain spiritual knowledge after my mission was studying the Seminary Teacher: Preservice Material in the Gospel Library. This helped me immensely after the mission to understand doctrine I studied every entry and highlighted it up and down. A lot of the material in the seminary teacher readings applies to missionaries too. It has really good information that all missionaries should know.
How to find Seminary Teacher Readings in Gospel Library
Studying these things will help guide you as a missionary so you will know how to teach with power and authority.
