Ok, cool. So you did the entire installation yourself? Including setting a password on the root account? Did you also add a regular user account? If not, you know you cannot login with root remotely, that's disabled. So you'll need to login on the console, that same console you used to install FreeBSD on that VPS.
Next time you do a FreeBSD install add a regular user and add that user to the wheel group. Then you can use that user account to login remotely, and because it's in the wheel group allow you to
su(8) to root.