i read alot of atricles taking about this but i could fix my problem yet .. i want to make the permlink custom
/%category%/%postname%
and i searched for the .htaccess in the wordpress files and i couldn't find it so i created one and added this code
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /sitename/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /sitename/index.php [L]
</IfModule>
# END WordPress
in the RewriteBase this name is the name of the folder of wordpress in my hosting , when i open my site the permlink changed as i want but when i open the page it gives me an error 404 Not Found error by the way i tried to choose the twentytwelve but its not working also , i added the .haccess file in the file mythemes in mytemplate is that the right place ??