A similar question has been answered through our website before! This post mentions that people can demonstrate citizenship by giving back to their community. Following the rules and laws of your country, state, or city, as well as volunteering and participating in community service efforts are ways to show that you are active in your citizenship. You might also participate in local government meetings or run for city council.
If you are old enough and live in an area where elections are held, voting is a great way to demonstrate citizenship. By voting, you are helping to shape the future of your nation, state, province, or city. Military service—especially when considered to be compulsory—is another way of demonstrating citizenship. Military service shows a devotion to one's land and a willingness to defend it, however, it is not available to everyone. People who are not of age or have physical or mental impairments can do their part by demonstrating citizenship in other ways.
This Australian website talks about the many ways in which people can demonstrate citizenship from a local to global level. I think this is an important perspective, because we are not just citizens of the places whose borders we live inside—all humans share the same planet and must work together to support each other. Organizations like Doctors Without Borders demonstrate global citizenship as opposed to just local or national citizenship.