How To Show Content To Logged In Users Only

Replace the whole body.html with below code.

{include file="$style_dir/global_header.html"}

{include file="$style_dir/header.html" }
{if userid()}
<div id="container">

    <!-- Message -->
    {include file="$style_dir/message.html"}

    {foreach from=$template_files item=file}
        {include_template_file file=$file}

{include file="$style_dir/footer.html" }
{elseif !userid()}
<div id="container">
<div class="alert alert-danger" role="alert">This page content is for logged in users only. Kindly login by pressing button in header or Create a new account by clicking <strong>Create New Account</strong></div>

If user is logged in it will show website content otherwise will urge user to either login or create a new account.