How do I select channels on Roku?

Can you guide me through the process of selecting channels on Roku? I'm new to this platform and a bit confused about how to navigate through the different options. I've heard that Roku offers a wide range of channels, but I'm not sure how to find and add the ones I'm interested in. Is there a specific method or sequence I should follow to add channels to my Roku device? Any tips or tricks you can share to make the process easier and more efficient?