Getting File/User Unavailable is usually just because that user has gone off line or in some cases it can happen if you wind up on the ignore list for reasons beyond your control or for not sharing enough files to meet that users particular settings..
Best thing is to either keep trying having your WinMX Settings for Auto Find Sources and Auto Enter Que set for your tastes.. or to find another source of the files.
There are no 'correct settings' for WinMX because there are a lot of different users and set ups out there. These settings depend on your Internet Connection type, Speeds of you Connection, whether you use primary or secondary on WInMX etc...
Here is a page that explains some basic 'To Dos' for most Broadband usershttps://www.winmxworld.com/tutorials/helping_winmx.html
and if your a Dial Up user have a look here:https://www.winmxworld.com/tutorials/set_up_for_56k.html
Im not sure what your asking about the MXMonitor program but if you want to learn how to set it up have a look here:https://www.winmxworld.com/tutorials/mxmoni.html
Dont worry about being a computer nerd.. we have lots of reading if you click the Tutorials link you see above here for help and how tos..