FoxyCart: Add Checkout Dropdown

<div class="fc-form-group ">
    <div class="col-sm-8 col-sm-offset-3" data-fc-error-for="referral_source" data-fc-error-class="fc-alert-container--error">
        <div class="fc-input-group-container fc-input-group-container--checkbox fc-input-group-container--active">
            <label class="fc-input-group-container__title fc-input-group-container__title--forced fc-form-label">
                Referred by… (required)
            </label>
            <div class="fc-form-group">
                <p>How did you hear about us?</p>
                    <select name="referral_source" id="referral_source" class="fc-form-control" aria-required="true" data-fc-required>
                    <option value="SOURCE_01" {% if referral_source == "SOURCE_01" %}selected{% endif %}>This Website</option>
                    <option value="SOURCE_02" {% if referral_source == "SOURCE_02" %}selected{% endif %}>Online Ad</option>
                    <option value="SOURCE_03" {% if referral_source == "SOURCE_03" %}selected{% endif %}>Email</option>
                    <option value="SOURCE_OTHER" {% if referral_source == "SOURCE_OTHER" %}selected{% endif %}>Other</option>
                    </select>
            </div>
        </div>
    </div>
</div>