Just add this line at the beginning of your .htaccess file which you can access by SFTP:
How to implement the 301 Redirect
1. To create a .htaccess file, open notepad, name and save
the file as .htaccess (there is no extension).
2. If you already have a .htaccess file on your server,
download it to your desktop for editing.
3. Place this code in your .htaccess file:
redirect 301 /old.html http://www.yourdomain.com/newURL.html
4. If the .htaccess file already has lines of code in it,
skip a line, then add the above code.
5. Save the .htaccess file
6. Upload this file to the root folder of your server.
7. Test it by typing in the old address to the page you've
changed. You should be immediately taken to the new
Notes: Don't add "http://www" to the first part of the
statement - place the path from the top level of your site
to the page. Also ensure that you leave a single space
between these elements:
redirect 301 (the instruction that the page has moved)
/old.html (the original folder path and file name)
http://www.yourdomain.com/new.html (new path and file name)
When the search engines spider your site again they will
follow the rule you have created in your .htaccess file.
The search engine spider doesn't actually read the
.htaccess file, but recognizes the response from the
server as valid.
During the next update, the old file name and path will be
dropped and replaced with the new one. Sometimes you may
see alternating old/new file names during the transition
period, plus some fluctuations in rankings. According to
Google it will take 6-8 weeks to see the changes reflected
on your pages.