Mostly need to watch wandavision. Some other stuff might provide a little bit of context, but most should make sense with Wandavision.

What you need to know going into WandaVision is: (Spoilers for inifinity wars and end game) - Wanda and Vision were deeply in Love - There was a plan to separate vision from the mind stone and save his life - Thanos came too soon, so Wanda had to keep Thanos at bay while destroying the mind stone from her beloved’s head and killing him - Thanos used the time stone to bring her love back to life - Thanos killed him in front of her - Thanos snapped her out of existence for 5 years - she’s back