Keeping A Steady Beat
The first way to use a metronome is to simply practice keeping the beat steady and avoid slowing down or speeding up. The metronome doesn't listen to you, so you'll have to listen to the metronome and try to stick with it. Let me show you how it works!
Set your metronome to a comfortable tempo which is 70 BPM. First we listen for the brighter click. That's beat 1. Now count along verbally. This is a very important step because you focus your attention on the metronome.
Try and strum your E minor chord as whole notes. Next up let's try half notes. Now let's try quarter notes, which will be every click. You can even try adding the 8th note upstroke in between.
Now you probably notice that it gets harder not to lose the metronome the more you play, and this is an extremely important lesson: in order to play music we have to learn to listen and play at the same time and the metronome is a great tool for practicing that.
So forget about the hard stuff and play as simply as you need to in order to be able to stick with the metronome. Again, this device is not going to listen to you like another human would so you have to focus all your attention on the metronome and constantly make little adjustments to stay with it, I call this surrendering to the metronome and it's a big first step towards learning rhythm.
Let's do a simple example with our E minor chord and the metronome at 75 bpm. As always, you're encouraged to just watch and listen, before you playing along yourself. And then afterwards I highly recommend you try it with a metronome on your own.