You can activate and deactivate any of Jetpack’s features by going to Jetpack → Settings.
Scroll all the way to the bottom of that page and click Debug.
Select the Access the full list of Jetpack modules available on your site link to open the list.
Here’s a handy GIF that shows the full process in detail:
Note that some features are activated by default when you first install Jetpack – you can always choose to deactivate them later if you wish.