First, convert your epub file to mobi. You can use calibre to accomplish that.
Then you need to upload your mobi file to Amazon. You can either do that by using Amazon's Send To Kindle app (
https://www.amazon.com/gp/sendtokindle) or by emailing the mobi file as an attachment to the kindle email address for one of your devices. The device email addresses should be listed on this page:
https://www.amazon.com/hz/mycd/digit...ily=KINDLE_APP
Once your file is in Amazon's cloud, it will be available for downloading on all your devices. On your devices, touch Library then All to see your books.