It seems like you're asking about "AtomVPN APK." However, I must clarify that "AtomVPN" is not a well-known or established app, and it might be a lesser-known or hypothetical app. It's possible that you may be referring to a specific VPN (Virtual Private Network) software or a custom-built application. If "AtomVPN" is a hypothetical or less-known app, I recommend verifying its name or features before proceeding. If it's a legitimate VPN service, I can provide general information about how to install and use it.