Start from the beginning.
About the hardware.
How many servo do you want to controll with the ESP32?
Do you already have the circuit (for example: which pins do you use on the ESP32)? The ESP32 is a 3.3V device. The S90 servo is a 5V device. Not sure if the servo works without level shifter.
First, try to build @Juan_Antonio Wifi example:
https://community.appinventor.mit.edu/t/esp32-wifi-webserver-led-on-off-static-ip-soft-access-point/9323/3
Tell us if you need help with this.