WandaVision was released in 2021 on Disney's own streaming service, Disney+. Since then, they've added a whole host of other shows based in the MCU, with several more in the pipeline. Currently, there are not any other sites where you can stream WandaVision. You can get a free trial of Disney+ on their website provided that you're a new customer, which should give you enough time to watch the series. However, if you don't have any intention of getting Disney+, you can also buy the DVD that Disney released for season 1.