You can expose a local device to the internet by setting up port forwarding on your home router, but this creates a security risk as it can make the device vulnerable to external attacks if not properly secured ➜ if you don't know what to do, you should probably do nothing as poking a hole into the security of your router opens your home network to hackers and bots' attacks....
which ESP, which router, which mobile app... Do yourself a favour and please read How to get the best out of this forum and post accordingly. More information is always better.