You can only login when prompted at the device when changing a thing that requires it.
You can only do the address book though when on the webpage, or from the tool I linked to directly in my post.
As for the admin account, it is simply admin with all lower case and no password, unless somebody there changed it. If that is the case the only way to fix that without having the new account info is to wipe the device, This will delete everything on the device and put it back to factory defaults, so your current address book and everything else will be lost entirely. Which is done at the control panel via System > Admin Menu > OK > Network Settings > OK > Initialize NVM > OK > Yes
By far your best option is to just download and install the tool from my initial post.