Being able to count music is not just for musicians--dancers, too, require the same ear to be able to fully utilize a piece of music or song to their advantage. Counting rhythm can vary in difficulty because some songs are very syncopated or in strange meters, but in general, if you develop your basic counting skills of whole beats and "and" beats, you will be able to apply your knowledge to any piece of music and perform your dancing at a higher level.
Understand the basics of rhythm. Music is mathematical and everything can be divided into even values. When you have a regular rhythm of a particular value (i.e. 1, 2, 3, 4), the beats in between those beats are the "and" beats and half the value (i.e. 1 and 2 and 3 and 4 and). Furthermore, these "and" beats correspond to transitional movements in dance. While we want to hit our feet and "lines" on the beats, the dancing itself happens in between the beats. An example would be a simple forward walk: if you want to arrive on time, you have to initiate a half a beat or a whole beat ahead of time so that you have sufficient preparation to get there on the beat.
Place the metronome on 60 beats per minute (BPM). This is slow enough to allow you to count "and" beats later on.
Using your hands, clap for every beat and count to 4 repeatedly until you feel confident in keeping that rhythm.
Place your hands between your knees. When you clap, you will hit the whole beats (i.e. 1, 2, 3, 4). When your hands release and separate, they should hit the insides of your legs/knees. These are the between beats, or "ands" (i.e. 1 and 2 and 3 and 4 and). Do this until the rhythm is consistent and you can reproduce it at will.
To verify if you are correct, you can always double the tempo of your metronome. So, for 60 BPM, you can put it up to 120 and see if your "and" counting was the right speed. Try to vary the tempos so that you can master this concept. Most music is faster than 60 BPM.