You can just say "I am writing to tell you about how I study English" or "I am writing about how I study English" As for your paragraph, here are some corrections I would do: I'm a big fan of the English show called EBSe 생활영어. They have two hosts that are from the United States and Korea. In the beginning of every show, they have a keyword to start the show and to help introduce the viewers to a new word. On the first section, the hosts give a hint through their speech to help the viewers guess what the keyword is. Next, they ask some questions about the word and then give some example answers to help the viewers learn some more English. On the third section, a native speaker tells a story that relates to the keyword. During this section, I memorize some English sentences that I think are useful. After, I try and translate the Korean subtitles into English. Finally, they show some example writing that includes a keyword from social media. I'm not sure what you meant by "I can't wait it" so I don't want to correct it into something that you don't mean. I hope this helps!

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There is no need to put either to tell or to say in that sentence.. you could just say: I'm writing about how to study english.