View file PF.Base/module/admincp/template/default/controller/trial/index.html.php

<div class="message">
    Upgrade your site to a Licensed phpFox version by entering your license ID &amp; key.
</div>
<form method="post" action="{url link='admincp.trial'}">
    <div class="table">
        <div class="table_left">
            License ID
        </div>
        <div class="table_right">
            <input type="text" name="val[license_id]">
        </div>
    </div>
    <div class="table">
        <div class="table_left">
            License Key
        </div>
        <div class="table_right">
            <input type="text" name="val[license_key]">
        </div>
    </div>
    <div class="table_clear">
        <input type="submit" class="button" value="Enter License Key">
    </div>
</form>