"the tunes I have that DO have metronome numbers on them indicate tempo with a quarter note symbol, an equal sign, and a number. If someone would post a clear explanation of the 'proper' use"

This is the normal proper use - if your metronome (I was brought up on mechanical ones that had a bell) has the extra facility of counting the beats in a bar, then you set that number to be the number of those specified beats to a bar.

There are a few tricks for learning very difficult pieces.

You can slow down the pace at first.

Also if the piece has lots of fast eighth notes, for example, you can set the pace at an appropriate rate, and set it to the eighth notes, as well as setting the correct number of those beats to a bar as the "bell sound" marking the start of a bar. So for a 4/4 time signature, temporarily pretend it is an 8/8, whatever.

If trying to practice Irish type music with a metronome, you should be aware that the beats do not come on the count as indicated, but 'bend' or 'swing' - if you haven't heard the music style, you won't learn it by yourself and by using a metronome.

Once you have some training, you should be able to keep the pace of 'Classical' Music internally, without need for a metronome, or any other external timing aid. And since much 'Folk Music' and 'Jazz' type music (also much 'ethnic' stuff) bends the basic 'Classical' beat, you will find it unuseful except for marking the basic start of bars anyway.

Robin