You will find or create an opportunity to help the environment in some way. You may opt to volunteer somewhere that allows you to actively/physically be part of something like a trash cleanup, or you could find a way to raise money for an organization that helps the environment in some way.
Make sure to let your parent(s)/guardian(s) know about what you're planning so they could get involved as well! Many of the volunteering opportunities with existing organizations require a parent chaperone if you're under the age requirements.