you can add this code to your lightbox code panel to do that using an onClick function
Login code:
import wixUsers from 'wix-users';
import wixLocation from 'wix-location';
//Add this code into an onClick function
let email = $w("#email").value;
let password = $w("#password").value;
wixUsers.login(email, password)
.then( () => {
console.log("User is logged in");
wixLocation.to("https://sewellstephens.com/dashboard"); //Change the URL ending to whatever page you want to send the user to after they log in.
} )
.catch( (err) => {
console.log(err);
$w("#errorMessage").expand();
} );