I've got both the Config and QtLockscreen itself installed, and know how to choose a new lockscreen. That isn't the problem I've described - it's trying to make edits to the ini file at all that I'm having trouble with.

It's no good knowing how to choose a new lockscreen when you can't get the lockscreen to look the way you want... all I'm trying to do is change the wallpaper of it.

I eventually tried doing it as sudo, but as I don't know the default sudo password, I hit a brick wall there too. And when I tried to get root, the terminal returned something about breaking the device - not exactly encouraging!

I'm getting quite frustrated now