Tic Tac Toe – minimax algorithm

I wanna use the minimax algorithm in tic tac toe. But I dont know how I could change my code. Right now the computer is choosing a random x on the board and checking if its available. I have read about it and seen some people do it but they have very similar code. I have a different one. I dont understand how to call the minimax on each available spot and the bestScore and bestMove stuff. this is my code now: check the snippet

const cellElement = document.querySelectorAll('[data-cell]')
const winner = document.getElementById("winner")
const winningConditions = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
]

let nextTurn = true
let win = true

function createCells() {
    cellElement.forEach(cell => {
        cell.addEventListener("click", cellButton, { once: true })
    });

}
createCells()

function cellButton(e) {
    const cell = e.target
    playerTurn(cell)
    checkWin()
    computerTurn(cell)
    checkWin()
    //check for draw
}

function playerTurn(cell) {
    if (nextTurn == false) {
        if (cell.innerHTML !== "✖") {
            cell.innerHTML = "Ｏ"
            nextTurn = true
        } else {
            alert("Choose another cell")
        }
    }
}

function computerTurn(cell) {
    let i = Math.floor(Math.random() * cellElement.length);

    if (nextTurn) {
        if (cellElement[i].innerHTML !== "✖" && cellElement[i].innerHTML !== "Ｏ") {
            cellElement[i].innerHTML = "✖";
            checkWin()
            nextTurn = false
        }
        return computerTurn();

    }
}
computerTurn()

function checkWin() {
    if (win) {
        for (let winCondition of winningConditions) {
            if (winCondition.every(i => cellElement[i].innerHTML == "Ｏ")) {
                winner.innerHTML = "O WON!!!"
                win = false
            } else if (winCondition.every(i => cellElement[i].innerHTML == "✖")) {
                winner.innerHTML = "X WON!!!"
                win = false
            }
        }
    }
}
body{
    background-color: #55E9BC;
    display: flex;
    justify-content: center;
}

.board{
    position: relative;
    width: 300px;
    height: 300px;
    top: 70%;
    display: grid;
    grid-template-columns: repeat(3, auto);
}

.cell{
    background-color:#11D3BC;
    color: #FFFCCA;
    width: 100px;
    height: 100px;
    margin: 1px;
    font-size: 80px;
    text-align: center;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
}

#winner{
    position: absolute;
    top: 250px;
    font-weight: bold;
    color: #3ab871;
    font-size: 40px;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
}
    <p id="winner"></p>

    <div class="board">
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
        <div class="cell" data-cell></div>
    </div>