I'm attempting to implement multisite to ensure that I'm able to add other blogs.

I added define('WP_ALLOW_MULTISITE', true); type of code in wordpress-config.php file under define('WPLANG', '');

After I consider the configure network panel I recieve this message:

"Since your install isn't new, the websites inside your WordPress network must use sub-domain names. The primary site inside a sub-directory install will have to make use of a modified permalink structure, potentially breaking existing links."

I would like my blogs to stay in sub sites.

Like : http://abcd.com/site1, http://abcd.com/site2, http://abcd.com/site3

What must i do to ensure that I'm able to proceed with setting up the multisite option using sub sites?

Thanks ahead of time