If your device is not rooted/jailbroken, you manually install a save file. Instead, use cloud saves:

the archive on your device or PC. You should see a folder named com.grimsoul.survival.game or individual .dat files.

To "install" this data on a new device, simply log in with the same account and tap Connect in the settings. The game will prompt you to load your saved progress. 2. Manual Local Backup (Android)

/data/data/com.grimsoul.survival.game/