If you have never made pull request to a free open-source project you should make that your weeks challenge. Even something simple, like fixing some spelling in a readme doc. Don't be scared. There's a bunch of technical ways to make a pr, but the easiest is to edit a doc directly in github, it will make the pr for you. Just register on github, go to the page you want to edit and click the edit button 👍. 
Even if your pr is rejected, you made a pr, well done, you are a modern human again, welcome to the revolution 🤝.