Hi! To write a letter to Taylor on Mogul, you would post your story at www.onmogul.com/post and then place it in the Taylor Swift hub when picking a category. The Mogul team will then be printing all the letters to send to her!
I know a little bit of android application development. Android Application Development needs the knowledge of Java language and Eclipse or Android Studio as an IDE.
You could check the following links if you want to learn from scratch how to build android applications:
1) Android Developers Platform-https://developer.android.com/index.html
2) JavaTpoint -http://www.javatpoint.com/android-tutorial
3) Tutorials Point - https://www.tutorialspoint.com//android/index.htm
4) There is a series of YouTube videos you can try to learn from them as well.
5) Do you know about Coursera? Try looking for free Android training in Coursera.