To get files from my computer to Kindle. I use email. Here’s how using Send to Kindle:
1. Go to Manage Your Content and Devices in your Amazon account. (This is assuming you’re using a Kindle or the Kindle app on another device of course.)
2. Hit the Settings tab.
3. Scroll down to Personal Document Settings > Send-to-Kindle E-mail Settings.
4. Copy the email address next to the device you want to send to.
5. Create a contact in your email client (Gmail, Yahoo, etc.).
6. Next time you want to read a document on your device using the Kindle app, simply email it as an attachment to that email address.