The deploy user's sudo password is emailed to you when your server gets created for the first time. 

This email might go to your spam folder, so check there if you didn't see it in your inbox. Keep this password somewhere safe as you'll need it if you plan to install software on your server.

Each server has a separate deploy user password to add some additional security.

You can login directly as the root user over SSH, without using the sudo password:

ssh root@IP

Or you can login as deploy and use sudo (which will ask for this password)

ssh deploy@IP
sudo su