I can't find any troubleshooting information for the SMBroadcast application which means that you will have to look in the installation folder of the software for the help guide. In that guide, you will find all the necessary information related to password changing and administration options.
I've looked on the web but couldn't find anything about it. If the software is still installed and you can open it, go to Help > Contents because that guide I was speaking earlier can be accessed in this way as well.