I received an e-mail today stating I can get Showtime free for a *-day trial. Then, if...

I received an e-mail today stating I can get Showtime free for a *-day trial. Then, if I want to keep it, it will be $**.** a month. What I need to know, is do I go right to the Showtime app or do I have to go through the Roku app to get to Showtime? If so, how do you do that. Also, I went to the Showtime app and it started to download ESPN and I don't want that and I'm afraid that's a pay channel and I had just updated my payment details and am afraid I'm going to be charged to ESPN and anything else it may have added that I did not want. Can you please advise me on all that I am asking and assure me there will be no charges for ESPN or any other channels that automatically began downloading when I went on to Roku which I did not mean to download, if in fact that it what happened. I appreciate your help and thank you in advance for your assistance and guidance.