How do I activate Roku on my TV?

Excuse me, could you please clarify the steps involved in activating Roku on my TV? I'm having some difficulty figuring it out and I would really appreciate your guidance. I've heard that there's a specific code or something that I need to enter, but I'm not sure where to find it or how to proceed. Could you walk me through the process step-by-step? Thank you so much for your help!