Hi TDRock,
You’ll need an FTP client and a text editor.
Once you have logged into your FTP server:
1) Go to /public_html/ if you have WordPress installed in your root folder. Or go to /public_html/wordpressinstall, where wordpressinstall represents whatever you named the subdirectory (folder) where you installed WP.
2) Find the .htaccess file.
3) Duplicate the file using your FTP client in case something goes wrong so you have a backup.
4) Right click and open the .htaccess file with your preferred text editor.
5) Copy and paste this code into the top of your .htaccess file
<Files "xmlrpc.php">
Order Allow,Deny
deny from all
</Files>
6) Save .htaccess file.
If you download the .htaccess file to your HDD before editing, you’ll have to re-upload via FTP to the appropriate place as outlined above.
If you are using Transmit FTP and CODA to make changes, saving right from CODA will automatically save the changes to the server so you won’t have to download/upload the file.
Hope this helps!