One time only.
Settings are saved in myviewer.ini.
Place MyViewer.exe in the directory where the regular ChunkViewer.exe is.
First time use it will give you a warning about missing files.
Don't worry those will be created when you close the app.
Next go to the settings tab and make your settings (quality, if you want autoscaling or not, LAN or outside repeater address, and password -optional).