Usually Joomla cannot display your website name after the title you have set for it. However it’s pretty simple to make it the way that you want.
There is a file named head.php in your joomla file structure. You need to find and edit this file. The path to this file is:
Open the file and find this line:
$strHtml .= $tab.'<title>’.htmlspecialchars($document->getTitle()).'</title>’.$lnEnd;
Now between <title> and </title> is the title of your website. ‘.htmlspecialchars($document->getTitle()).’ is the php code that helps Joomla provide the title you have set in the control panel. Now you can simply put something after or before it. For example:
$strHtml .= $tab.'<title>’.htmlspecialchars($document->getTitle()).’ – OSGuides.net</title>’.$lnEnd;
This makes the title looks just as OSGuides.net is currently. Once you save the file with the new changes it should work.