pyforum comes by default with an administrator's account pre-set, this account is administrator||at||pyforum.org and a randomly generated password for each installation.

If you wish to use your own "Administrator" account, the recommended way of doing this is by:

Create a brand new account (which will have regular Member roles
Log out and log back in with the administrator||at||pyforum.org default account.
Go to forum administration, click on the "Users" tab, then select the user you wish to give administrative permissions to.
Grant "zAdministrator" role to the user and save his/her profile.
You may now log in as the changed user and even remove the original administrator account.

If you lost the default Administrator's password

Passwords are stored hashed and salted in the DB, you can change a password for any account in auth_users to anything you want, for example, if the auth_email field in the auth_users table is "user@example.com" and you want to assign the password "DeepSpace9", log into python and follow the example below:

rotarran:~ julio$ python
Python 2.7.1 (r271:86832, Jun 16 2011, 16:59:05) 
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> auth_email = "user@example.com"
>>> password = "DeepSpace9"
>>> import hashlib
>>> hashed_password = hashlib.sha1('%s%s' % (auth_email, password)).hexdigest()
>>> print hashed_password
de2ad63f4deab14e8f33152fc88e2916b87c8a81
>>> 

In this case, the hash de2ad63f4deab14e8f33152fc88e2916b87c8a81 is the piece of data that you should store in the auth_user table for the auth_passwd field.