Open the app and connect. Some apps allow you to choose servers and use tweaks. To make sure you get the right file, let me know: amtunnel config files for Mobilis specifically? Is your device Android ? APNA TUNNEL LITE - Apps on Google Play
These apps often require a specific .amtunnel or .mltunnel configuration file tailored to Mobilis network settings to work.
Another popular option from the same developer.
Alternative source to download the XAPK/APK file directly. Key Details for Setup
Download the app, and if using an XAPK file, you may need to enable "Unknown Sources" in your Android settings.
A fast, free VPN often used for network tweaks.