Internet gives you access to so many things that it's hard nowadays to live without. The proof being that you're reading this right now.
But if you don't want to contribute to the system in place how can you use it's infrastructure?
Free wifi is the first solution. It's common to find one but you can install an app on your phone to find them more easily.
Once you find it, you can connect to it with your computer or phone.
When you are on a free wifi, your traffic is not secured. Keep this in mind all the time. Solutions exist (like VPN) to avoid this constraint and bring security back.
Restaurant, cafes, libraries or train stations are some of the common places for you to find free wifi.