Login to Amazon and go to manage your content and device section from your account.
Click on the device tab, after clicking on device tab you will see the below screen. This screen will show you all your kindle apps and at the last your Kindle email address. Using this kindle email address you can push your document to Kindle. For that you have to also set the authorized sender so that email with attachment only with those email address will be get pushed into your Kindle app.
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| Kindle email address screen |