Go to your device's Settings > Security (or Lock Screen and Security on some devices) and enable "Unknown Sources" or "Install unknown apps." This option allows you to install apps from outside the Google Play Store.
Since this is a third-party application, it is not available on the official Google Play Store. You must: Enable Unknown Sources Smart Youtube 6.14.18 Apk
Version 6.14.18 is often cited by the community as one of the most stable builds of the original "Smart YouTube TV" series before the developer transitioned focus to the newer "SmartTubeNext" project. Go to your device's Settings > Security (or