Firstly, please check the device whether to support the Alexa, as shown below, in the Produts--Smart Products, you could confirm it.
If your device doesn’t support it, you could click the Value-added Services —— Smart Speaker to apply the Alexa Access fucntion.
If your device supports the Alexa, please choose it on the left side, and sign in the skill name on the right side. (if you customize private brand skill, you can fill in your brand’s skill name; If you haven’t customize this skill, please buy it in increment service market and customize it.OEM Amazon Alexa Skill)
Displayed on the Mobile App
With above steps completed, please re-build your app. After App finished, you could scan the QR Code in the page to download and see the effect. When the fuction is on, Alexa would showned in the more service on the App page.