How to Enable ADB on an Amazon Fire Tablet

Step1: First, you’ll need to dive into the Developer Options menu, which isn’t visible by default. To get there, open the “Settings” app on your Fire Tablet.
Scroll down until you see “Device Options” or “About.” Tap on it.

Step2: Within the “Device Options” or “About” menu, look for the “Serial Number” entry. If your Fire Tablet has the “Device Options” menu,
you’ll need to go to “About Fire Tablet” first. Tap on “Serial Number” repeatedly, about seven times. You should see a notification pop up saying, “You are now a developer!”
or similar. This unlocks the hidden Developer Options.

Step3: Now that you’re a developer, go back to the main “Device Options” menu. You should now see a new entry called “Developer Options”
toward the bottom of the list. Tap on it. Inside the “Developer Options” menu, find one of either two options, depending on your Fire Tablet model. “USB Debugging”
(8th Generation or newer) or “Enable ADB” (7th Generation or older). Toggle the switch next to it to the on position. You might see a prompt asking you to confirm
that you want to allow debugging; tap “OK.”

You are now ready to connect your Fire Tablet to your computer to use ADB.
You can use ADB to control your Fire Tablet over USB from a computer,
copy files back and forth, install and uninstall apps, run shell commands, and more. One particularly useful ability for Fire Tablets

Credit : https://www.howtogeek.com/how-to-enable-adb-on-an-amazon-fire-tablet/