i created droplet but when i tried to access to this ip http://184.108.40.206/ in my browser
i get this message "Please log into your droplet via SSH to configure your LEMP installation."
i don't know why i can't acces...
This is only a bad formulation of message. It's static message that you can see in /var/www/html/index.html.
Open it if editor you like, e.g.:
Observe it and you will notice that...