Unknown directive when adding a new default page in nginx

I am using nginx to host a website and following is the current configuration which is defined at /etc/nginx/sites-available/mysite

Config

server {  
   listen 80;  
   root /var/www/mysite;  
   index.php index.htm index.html;  
} 

Problem is as soon as I set another page as default nginx start throwing error

unknown directive "somepage.php" in /etc/nginx/sites-enabled/mysite

New Config

server {  
       listen 80;  
       root /var/www/mysite;  
       somepage.php index.php index.htm index.html;  
    }

I don't understand what am I doing wrong here. Can you please check?