Follow these steps to sign in:

Navigate to the Apps tab on the TV’s Home Menu and select See all → TV Control with Smart Speakers.
When the Account logged out screen appears, select OK.
Follow the on-screen instructions to enter the activation code shown on the TV into your mobile device.
Once the activation code is confirmed, tap Proceed to complete the sign-in process

Sign in using the ID you’ve been using previously, whether it’s your Sony account ID or an Amazon, Apple, Facebook, or Google ID.

When you choose an Amazon, Apple, Facebook, or Google ID, the migration to your Sony account will start. Follow the on-screen instructions to complete the process.
If you’re unsure which account you used to sign in, try logging in with your Sony account on the sign-in screen first. You can also check the article “If You Don’t Know Which Account You’re Signed In With” for more guidance.

After signing in, you will need to enable the link to the Amazon Alexa app* on your smartphone. Follow the steps below to complete the process:

Open the Amazon Alexa app on your smartphone.

When the Sony TV skill screen appears, tap “Enable to use.”

Follow the on-screen instructions to link the account you’re signed into on the TV to the Sony TV skill. Once the process is complete, the message “Your BRAVIA account has been successfully linked” will appear. Tap “Close.”

*The Amazon Alexa app is a mobile application provided by Amazon.