https://arduino.stackexchange.com/questions/78552/wiring-up-an-esp-01-to-nano?answertab=votes#tab-top

https://www.electronicslovers.com/2017/11/learn-how-to-setup-wifi-module-esp8266.html

https://www.youtube.com/watch?v=YKn2ZXYb_EI

arduino nano esp8266 esp 01 wifi

use buck converter (LM2596) for 3.3v

• There is a bug in the code:
• SoftwareSerial softSerial(3, 2); RX, TX * should be * SoftwareSerial softSerial(2, 3); RX, TX
• Also the suggested baud rate of 9600 doesnt seem to work, adjust to 115200 and go from there. Once you get a receiving signal, run the following to adjust the 01's baud to 9600:
• AT+UART_DEF=9600,8,1,0,0
• After this, reflash your nano with serial bauds set to 9600 and you should be able to send AT commands over your Nano to the ESP-01 via 9600 baud

#include <SoftwareSerial.h>
SoftwareSerial softSerial(2, 3); // RX, TX
 
void setup() 
{
  uint32_t baud = 9600;
  Serial.begin(baud);
  softSerial.begin(baud);
  Serial.print("SETUP!! @");
  Serial.println(baud);
}
 
void loop() 
{
    while(softSerial.available() > 0) 
    {
      char a = softSerial.read();
      if(a =='\0')
        continue;
      if(a != 'r' && a != 'n' && (a < 32))
        continue;
      Serial.print(a);
    }
    
    while(Serial.available() > 0)
    {
      char a = Serial.read();
      Serial.write(a);
      softSerial.write(a);
    }
}

• AT – Will give OK on the serial monitor, if Not just unplug vcc Pin of ESP8266 Module for a moment and reconnect again.
• Send AT+RST – Command to Restart module / Optional Command
• Send AT+GMR – To get the firmware version
• Send AT+CWMODE? – Set Module to a Dual Mode Sucha as Standalone + Access Point mode.
• Send AT+CWLAP – Command to Search Nearby Wifi Access Point. Find your Wifi Name in the Search Result.
• Send AT+CWJAP=”Your Wifi Name”,”Your Wifi Password” – Command to Connect to WIFI.
• Send AT+CIFSR – Command to Check Allocated Ip given by your Wifi to your ESP8266 Module/Optional Command.