There are various ways to accomplish what you want, but see if this works for you:
- Click Start, type autoplay in the Search box, and press Enter
- Next to the appropriate device or media type (see screenshot below), click the drop-down menu and select the action you want to happen as the default (see the second screenshot below, although you likely will not have the same selection of options).
- There are more media types and devices as you scroll down the window
- After you've made your selections, click the Save button and close the window (if it doesn't close automatically)