Go to: Settings > Security > Unknown Sources
This option may be located in different places depending on your Android version. Some newer devices require allowing installation from your browser specifically.
Open your file manager and navigate to the Downloads folder
The file name might show as "ssbet77" with the .apk extension
Tap on the APK file to start installation
Review the permissions requested by the app, then tap "Install"
Installation Successful!
You can now open the SSBet77 app from your home screen.