A .htaccess is simply a text file that provides commands to control a web site. You can put your .htaccess in any directory and changes applied to the file will effect the directory it is placed in, as well as all sub-directories.
To create a .htaccess file use a text editor (ie. Notepad) to create a file called .htaccess. When saving, it may append a .txt to the end of your .htaccess file but you can use an FTP client to remove that. Be sure to save it as plain text, not rich text format. The file should simply be called .htaccess when you upload it.
Please check the article “Using a .htaccess” for more specific information on its use.
Important Note: Creating and editing .htaccess files should only be done by skilled users. You can cause your web site to go down if you make incorrect changes to your .htaccess file.