A "code kata" is a small, isolated programming challenge that you can do for practice. There are many web sites that offer these. The best of them is Code Wars. There are many challenges for beginners, and as you get better at solving challenges, you will rank up into harder challenges.
There's no shame in skipping a challenge, but do try not to "cheat" and look up a complete answer. Come back to it later.
Sign up on codewars.com using your github account, and practice!
Try to do at least one every day, forever.
If (and only if!) you have finished all of the codewars exercises, you can also try the Ruby Koans. They will cover some topics that have not been taught explicitly, and for those you can either skip them, or (preferably) do some reading online and learn more about that topic.
The Koans are challenging, but also teach you a bit about the topic of testing. The way they are structured, you run the main script and it will show that the Koans are currently "failing". This means that the tests are not working yet -- so your job is to update the code for each Koan to make each test pass. This process is called test-driven development. We will cover this topic more in future lectures, so for now just focus on learning and practicing your Ruby skills.
Check it out: http://rubykoans.com/
