Hm, I set up pmachine a long time ago, knowing essentially nothing, and it installed like a (pleasant) dream. Did you try just leaving it blank or accepting the default?
I’m a little suspicious because the usual four things to ask for are database name, hostname, username, and password.
As to pmachine itself, I’m not very imaginative with templating and page design and only reluctantly stumble my way through core file customization, but pmachine has served me well for the use I put it to (private site for a dog club). It’s had very few security updates, the few upgrades I did were very easy, the admin section is nice, etc. You need to run php as cgi for the file browser to work. (Search for kb article “php as cgi” or just set that option in your domain control panel.)