How to clean url wordpress

[admin]

I'm using wordpress for a site,

this url before tes.com/index.php/about/
i want url like this tes.com/about/

I have tried copying parts of WordPress' .htaccess, however shows a 404 error.

My .htaccess file looks like:

# BEGIN WordPress
 <IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteBase /
  RewriteRule ^index\.php$ - [L]
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule . /index.php [L]
 </IfModule>
# END WordPress

Any ideas on where to start and how to accomplish what I'm looking for?