There's a statement describing this givaway (thank you HP!) "If you are interested in participating in this contest, I suggest you subscribe to this topic" - HOW?

Unless I'm wrong, I think this subscribing means staying up-to-date so as to successfully participate in the contest... i.e. to know the latest details. And you subscribe as you would subscribe to a normal topic.

On the top right corner of the post, click Options --> Track this topic --> Select your preferred method --> Proceed

From New User Orientation Forum: Is this topic, which addresses your question, I believe:How To Subscribe To An Existing Topic So You Are Notified When There Are Replies