For learning the fights in Tomb of Sargeras, start with the in-game dungeon journal. Then head to some out-of-game Tomb of Sargeras specific resources. Here are some of the ones I used, in rough order from least to most-detailed:
Detailed video guides will likely become available in the next week. Several folks made some handy weakauras for Tomb, such as these. I also did personal preparation like I did for Emerald Nightmare. Check out that article for general preparation tips applicable to all tiers. Good luck with the raid!