iOS v16 and lower / iPhone X and below:
 - Connect to WiFi
 - Open Safari and 
click here
 - Download and install profile
 - For iPhone X:
     - Settings > General > Profiles > Install
     - Enter passcode > Confirm Install
iOS v17 and up / iPhone XS/XR and newer: - APN auto-configures
 - iOS 18.5+: "Use Carrier Settings" enabled by default
Troubleshooting: 1. Settings > Cellular > Select SIM
 2. Enable "Use Carrier Settings" 
 3. Confirm setting turns green