Rotary Encoders

I have a few of these: https://smile.amazon.co.uk/KY-040-Encoder-Development-Arduino-including/dp/B09726Y8RB – five for under a tenner.

Wiring

Wiring diagram Rotary Encoder Wiring

From left to right, looking down the encoder from above, with the connections below:
GND   --> GND on Arduino
VCC   --> 5V on Arduino
SW    --> (switch) to digital in
DT=B  --> (rotary B) to digital in
CLK=A --> (rotary A) to digital in
So you need two digital inputs per rotary, and one per button.

Code

From https://lastminuteengineers.com/rotary-encoder-arduino-tutorial/

// Rotary Encoder Inputs
#define CLK 2
#define DT 3
#define SW 4

int counter = 0;
int currentStateCLK;
int lastStateCLK;
String currentDir ="";
unsigned long lastButtonPress = 0;

void setup() {

    // Set encoder pins as inputs
    pinMode(CLK,INPUT);
    pinMode(DT,INPUT);
    pinMode(SW, INPUT_PULLUP);

    // Setup Serial Monitor
    Serial.begin(9600);

    // Read the initial state of CLK
    lastStateCLK = digitalRead(CLK);
}

void loop() {

    // Read the current state of CLK
    currentStateCLK = digitalRead(CLK);

    // If last and current state of CLK are different, then pulse occurred
    // React to only 1 state change to avoid double count
    if (currentStateCLK != lastStateCLK  && currentStateCLK == 1){

        // If the DT state is different than the CLK state then
        // the encoder is rotating CCW so decrement
        if (digitalRead(DT) != currentStateCLK) {
            counter --;
            currentDir ="CCW";
        } else {
            // Encoder is rotating CW so increment
            counter ++;
            currentDir ="CW";
        }

        Serial.print("Direction: ");
        Serial.print(currentDir);
        Serial.print(" | Counter: ");
        Serial.println(counter);
    }

    // Remember last CLK state
    lastStateCLK = currentStateCLK;

    // Read the button state
    int btnState = digitalRead(SW);

    //If we detect LOW signal, button is pressed
    if (btnState == LOW) {
        //if 50ms have passed since last LOW pulse, it means that the
        //button has been pressed, released and pressed again
        if (millis() - lastButtonPress > 50) {
            Serial.println("Button pressed!");
        }

        // Remember last button press event
        lastButtonPress = millis();
    }

    // Put in a slight delay to help debounce the reading
    delay(1);
}