Simple Machines Forums are not Search Engine Friendly in their normal state, but Simple Machines can be tweaked to for SEO.
Removing the text Index that appears in your SMF homepage can be a first step to making SMF search engine friendly.

How to Remove Index from Title in SMF

– Login to your Control Panel, then locate the directory where your SMF was installed.

– Locate the “index.template.php” for the current theme you are using on yor forum. It can be founs at public_html > Themes > Your theme Name > index.template.php.

– Now edit it and search for

echo '
<meta http-equiv="Content-Type" content="text/html; charset=', $context['character_set'], '" />
<meta name="description" content="', $context['page_title_html_safe'], '" />', !empty($context['meta_keywords']) ? '
<meta name="keywords" content="' . $context['meta_keywords'] . '" />' : '', '
<title>', $context['page_title_html_safe'], '</title>';

And replace with

if ($context['page_title_html_safe'] == 'YOUR SITE TITLE - Index')
{
echo '
<title>YOUR SITE TITLE </title>
<meta name="description" content="META DESCRIPTION"/>
<meta name="keywords" content="META KEYWORDS "/>';
}
else
{
echo '
<meta http-equiv="Content-Type" content="text/html; charset=', $context['character_set'], '" />
<meta name="description" content="', $context['page_title_html_safe'], '" />', !empty($context['meta_keywords']) ? '
<meta name="keywords" content="' . $context['meta_keywords'] . '" />' : '', '
<title>', $context['page_title_html_safe'], '</title>';
}
.

That’s it. Check the title of your forum, it’s changed. Drop your comments if you need any help.