When you insert the video, Powerpoint should give you the option to have it automatically play or not. (I can’t give you a more precise answer, even though I wish I could, because I’m running Powerpoint for Mac, which is very different from Powerpoint for Windows!) IIRC, however, there should be something in the “pane” on the right-hand side of the screen that has to do with “Custom Animation” (might have to choose from a pull-down at the top). There’s a button or two on there that fiddle with the settings of the object in question. (Also, right-clicking and selecting, um, “Object Settings” (??) should give you a window that will allow you to fiddle with it.) Wow, I’m extraordinarily unhelpful, aren’t I?