<p id="myParagraph"></p>
<script> require("./renderer.js"); </script>

const mainWindow = new BrowserWindow({...});
mainWindow.loadFile("./index.html");
// ... later we get the `accessToken`
mainWindow.webContents.send("got-access-token", accessToken);

ipcRenderer.on("got-access-token", (event, accessToken) => {
    document.getElementById("myParagraph").innerText = accessToken;
});