You can do this simply following these steps:
- Go to Settings -> My Fire TV -> About -> Network and make a note of all the settings there (taking a photo with your phone is an easy way to do this).
- Go to Settings -> Network and select your Wi-Fi network. Click the remote's menu button (☰) to forget this network.
- Click on the connection again and enter your network password (SSID). Instead of clicking Connect, click Advanced.
- Enter the "IP address"...
- ... and "Gateway" values you noted in step 1.
- For Subnet Mask there can be a few options: enter 24 if the Subnet Mask value you noted in Step 1 was 255.255.255.0, or 32 if the "Subnet Mask" value was 255.255.255.255. For any other Subnet Mask values, use this tool to calculate the number. The value listed after Mask Bits is the one you are looking for.
- Enter the primary (DNS 1) and secondary (DNS 2) DNS settings.
Now you have changed the DNS in your firestick.
