Add &confirm=1 after the url
<p>
{if true}
<h3><a href="{'guest_register_confirm.php'|NwaGetAppUrl:false:$u.require_auth}?{if $u.source}gsr_id={$u.source|rawurlencode}&{/if}token={$u.register_token|rawurlencode}&confirm=1" target="_blank">click here</a></h3>
{else}