I am able to change the Default Lister but if I click on My Lister a different Lister appears.
I have tried searching in help but nothing comes up.
I take it Default Lister and My Lister are supposed to be different.
If so, could you please tell me how to change the setup for My Lister.
"My Lister" isn't part of the default configuration. It must be a layout or style which you've saved yourself.
If it's a layout, simply save over it with the new layout that you want. (Settings > Lister Layouts)
For a style, you can update it in various ways, depending on exactly what you want to change.