xml is your config file, you will find it in the Mach3 folder, it will be called Mach3Mill.xml if you are using the standard profile, if you have a custom profile then it will have the name of the custom profile.
You will need to copy it to your desktop and rename it to woodenbug.xml or something like that as the forum will only accept a file name once and Mach3Mill will already have been attached.
Hood