First, go here:
http://custom.simplemachines.org/mods/index.php?mod=36Where the link is to download the mod, you should see manual install instructions. Choose the one for 1.1.5. Find the changes needed for the index.template.php and do what it says.
Where it says to add some code before the // Search comment, change the code from this:
echo ($current_action == 'arcade' || $context['browser']['is_ie4']) ? '<td class="maintab_active_' . $first . '"> </td>' : '' , '
<td valign="top" class="maintab_' , $current_action == 'arcade' ? 'active_back' : 'back' , '">
<a href="', $scripturl, '?action=arcade">' , $txt['arcade'] , '</a>
</td>' , $current_action == 'arcade' ? '<td class="maintab_active_' . $last . '"> </td>' : '';
Add this instead:
// Show the [arcade] button.
echo '
<li><a href="', $scripturl, '?action=arcade">' , $txt['arcade'] , '</a></li>
<li class="mainnavDivider"><!-- /--></li>';
The real hell is your life gone wrong.