htaccess permissions – do I need to change them?

Hello, when I try to change my post URLs to /%postname%/, I get an error message that says my htaccess file is not writable. However, when I go into cPanel, it says the permissions are set at 644, which should be OK. Furthermore, the change to /%postname%/ has actually gone through, so that my post URLs are now “mysite.com/postname/.”

But the error message instructed me to change the htaccess as follows:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

———————-

My current htaccess looks like this when I put it into a text file:

# -FrontPage-
IndexIgnore .htaccess */.??* *~ *# */HEADER* */README* */_vti*
<Limit GET POST>
order deny,allow
deny from all
allow from all
</Limit>
<Limit PUT DELETE>
order deny,allow
deny from all
</Limit>
AuthName mysite.com
AuthUserFile /home/myusername/public_html/_vti_pvt/service.pwd
AuthGroupFile /home/myusername/public_html/_vti_pvt/service.grp

——————–

So the question is, where do I put these commands, if they really are necessary? Or is this error message simply a bug in WordPress?