Go get an FTP program like Filezilla ( http://www.filezilla.com ) and then connect to your FTP Server and upload the files to your /public_html folder. I hope this helps
Create those file and upload to the root directory of your site via FTP... If still have problem, then explain your problem in more details so that others can help you.
just open your server and take total site Backup now go to source page and edit it and add in before of body tag inside of header tag like this <head> <meta name="keywords" content="keyword, key keywords, etc" /> </head> that's it if you feel your site is not good or any problem just upload your old files
it's depends upon your site, if your site made in Opensource software like ... Joomla, drupal or wordpress, so you can follow these methods for adding meta tags and other tips are above