Hello, your ESP32 will need to run in station as well as access point(AP) mode
in access point mode ( with static IP address: [login to view URL] ) so user can connect to it, ESP32 will host a web page user can get access to it, web page with UI having textboxes for you to insert WiFi SSID, Password, your MQTT parameters , etc
the web page will let you save your settings into ESP32 EEPROM to be remembered each time your ESP32 boots
i can accomplish your task in couple of minutes if you award it to me
send me a message on chat so i take it on
Regards