The major format for reading on Kindle devices or app is MOBI. Therefore, you need to convert EPUB to MOBI and send result to the Kindle account via function “Send to Kindle by E-mail”. For that you need send mail with MOBI to e-mail: [name]@kindle.com (this e-mail you can find in the Kindle application settings) After MOBI was sent, he will be added to your account automatically.