In a browser
Go to the my IP page. Read the large address and press Copy address. That works on a laptop, a phone, and a tablet. You do not install an app.
Wi-Fi and mobile data
The IP address can change when you leave Wi-Fi and use mobile data. Check again after you switch. If a VPN is on, the address belongs to the VPN. The VPN check explains that badge.
Looking up another address
An IP address lookup for a different public address is on the IP location page. Paste the address and the map moves to that network.