Before installing, go to your phone's Settings > Security and enable "Install from Unknown Sources."

The application claims not to collect or share any data. Requirements: Requires Android 6.0 or higher.

Click the download button for the version (e.g., 1.55.3) that matches your device architecture.

For the safest installation, it is recommended to use reputable third-party app repositories if you cannot download it directly from Google Play.

Are you trying to fix a or just wanting to save battery? What Android version is your device running? I can provide more tailored steps for your device's setup. Killapps - Close Running Apps - Apps on Google Play

Some features, such as closing system apps, may require the paid Pro version.