Not able to get 2nd blog to format same as first blog

I have finally managed to get two blogs on my website. I want both of the blogs to have the same theme so that if I make changes to one everything will update accordingly.

I had the two blogs added via two installations. It seems like this is the reason why I cannot get the blogs to be under the same format. So, I went in and deleted the second installion but now I just get an index page with a parent directory link.

I tried to go in and add a second wp-config file but I dont know where to add it exactly. Plus I dont understand what I have to change.

I think this is the section I have to change. Under DB_name can I just add mysite_com/2ndblog?? and then $table_prefix change that to wp_xxx2ndblog??
‘
// ** MySQL settings ** //
define(‘DB_NAME’, ‘mysite_com/’); // The name of the database
define(‘DB_USER’, ‘XXXXX’); // Your MySQL username
define(‘DB_PASSWORD’, ‘XXXXX’); // …and password
define(‘DB_HOST’, ‘mysql.mysite.com’); // …and the server MySQL is running on

$table_prefix = ‘wp_xxxx_’; ‘

Any guidance would be appreciate. I hope to not have to just manually make all the changes every time. Thank you all!