There should be a file titled "Index.hmtl" within the "www" folder inside the web version you have downloaded. Double clicking this should open it in your browser, or you can drag it onto your browser instead. You will probably also need to follow the instructions of this link if you've never played an RPG Maker MV game through a browser before. https://www.reddit.com/r/RPGMaker/comments/dqvdqo/fix_error_failed_to_load_dataactorsjson/