To update your device's software version, go to Settings on your TCL Fire TV.

Check for available and performing Software Update

Ensure your TV is logged into your Amazon account
From your TCL FireTV Home Screen, go to:
Settings > Device & Software > About > Check for Updates
If an update is available, select Install 
Once update is complete, select Reboot
After rebooting, go back to Settings > Device & Software > About
To confirm the update finalized, you'll see “Your FireTV is up to date”.