Here you go...... You just have to use window.location dom manipulation function of javascript to redirect the user. You can use if-else statement to check which site was selected using querySelector or by any other means. Here is my code for it.

<form>
    <input type="radio" name="site" id="google" /> Google <br />
    <input type="radio" name="site" id="facebook" /> Facebook <br />
    <input type="radio" name="site" id="yahoo" /> Yahoo <br />
    <input type="radio" name="site" id="twitter" /> Twitter <br />
    <hr />

    <button type="submit" onclick="redirect()">Click to go</button>
</form>

javascript code below :-

function redirect() {
        if (document.getElementById('google').checked) {
            document.write("Redirecting...");
            window.location = ("https://www.google.com");
        }

        else if (document.getElementById('facebook').checked) {
            document.write("Redirecting...");
            window.location = ("https://www.facebook.com");
        }

        else if (document.getElementById('yahoo').checked) {
            document.write("Redirecting...");
            window.location = ("https://www.yahoo.com");
        }

        else if (document.getElementById('twitter').checked) {
            document.write("Redirecting...");
            window.location = ("https://www.twitter.com");
        }

        else {
            return;
        }
    }