SSh client could not changed "root" account,Why?

I have just installer DirectAdmin onto my server for FreeBsd v5.5. And I got this big problem.
Before I installed I had a user name and a password that worked.
After I have installed my username seems to work,but not the password.
When I login admin account into SSH client is fine, but could not changed "su root" account. How do I for that? Help me

I don't know why reinstalling DA would change the root password; I've never seen it care about the root password.

You'll need to boot your FreeBSD locally, in a mode that doesn't require a password, and then run the passwd command for root.

I don't know the details because I don't run FreeBSD servers.

Jeff