To choose the data, click on the Map Settings button in the bottom right hand corner of the map.
If your window size is large enough, you have quick picks available along the right edge of the map. You can configure these by opening map settings and then with a click and hold, drag a data layer/overlay or watch warning to a position in the quick picks area at the top of the Map Data page. If you prefer to have more map space, you can delete all your quick picks.
You can modify the map type you are using from within the Map settings area.
Any layer can have its transparency setting modified by using the transparency setting just to the right of the layers label in the map settings page.
Many of the data layers on the map can be animated by tapping on the play button at the bottom left of the map. The speed of the play can be adjusted by tapping on the 1x/2x button. For any data that can be animated, you can also drag the play head along the timeline to move to a specific time.