How to turn Html.BeginForm into Ajax.BeginForm

The following works, but how do I convert this to an Ajax Call?

<section id="loginWindow">
@using (Html.BeginForm("Login", "Account", new { ReturnUrl = ViewBag.ReturnUrl })) {
@Html.AntiForgeryToken()
@Html.ValidationSummary(true)

<fieldset>
    <legend>Log in Form</legend>
    <ol>
        <li>
            @Html.LabelFor(m => m.UserName)
            @Html.TextBoxFor(m => m.UserName)
            @Html.ValidationMessageFor(m => m.UserName)
        </li>
        <li>
            @Html.LabelFor(m => m.Password)
            @Html.PasswordFor(m => m.Password)
            @Html.ValidationMessageFor(m => m.Password)
        </li>
        <li>
            @Html.CheckBoxFor(m => m.RememberMe)
            @Html.LabelFor(m => m.RememberMe, new { @class = "checkbox" })
        </li>
    </ol>
    <input type="submit" value="Log in" />
</fieldset>

}
</section>