HELP! I can't enable a root user!

So I bought a macbook off one of my friends and was able to rename everything except for the home folder.

I've read that I needed to enable a root user. After following the instructions provided by everyone here, I've discovered that I'm missing my directory utility and I don't have a netinfo manager either. My mac is running on a Mac OS 10.5.8

I tried searching for it in the log in option in users but there is no "join" button everyone keeps speaking of.

I tried searching for the directory utility in the help bar but when I clicked on the steps it said "application was removed or uninstalled".

I'm beyond frustrated with this thing and any helpI get would be wonderful!