The phrase "kids are the future" is thrown around all the time. As a kid your automatic response is almost always "well yeah." You figure eventually your age group is going grow up to become the people in charge. It might take a while, but you'll get there. As someone quickly approaching the end of their teenage years I think we sometimes get this idea that once we are older is when we will really be able to do something about the issues that are important to us. You hear people say "when I'm older I'll do x, y, and z."
What you don't realize is you can start to make those changes right now. When controversial topics arise you hear a lot of "call/email your representatives to make sure they're voting the way you want" or something along those lines. People my age tend to kind of scoff and roll their eyes at it. You get the "that doesn't really help" response or "yeah, no I'm not doing that." If you're not old enough to vote yet that is one of the easiest ways to get involved. Go to marches for the issues you feel strongly about. Get involved in organizations that support the same ideals you do. Be outspoken on the issues that are important to you. Engage in conversation with other people about controversial topics, but also recognize that one conversation probably isn't going to change their outlook on life.
It is so very important to vote in every single election, not just the presidential election. You have to work from the ground up. If you don't approve of the way someone in office is conducting themselves, show up to the voting polls the next election.
Without fail during every single election you will hear people say that they're not voting because their vote doesn't count. THAT IS NOT TRUE. If you're saying it then chances are a lot of other people are too. You have to vote because who you put in office can and will change America, be it for better or worse, over the following four years.
GO VOTE!