I think it is very simple, it is just not easy.

This is how I do it. I sit down in a comfortable chair, feet flat footed on the floor, back fairly straight, and close my eyes. Then I focus all my attention on my breathing. Notice how your muscles move up and down. Is it up in your chest. Focus on feeling your breath going in and out of your lungs. If your attention wanders just calmly bring it back to your breathing. If thoughts intrude don't fight them just watch them come and go and bring your attention back to your breathing. Your attention will wander all over the place and your thinking will be all over the place. Each time you notice that your attention has wavered just calmly bring it back to your breathing. You will notice that your breathing gets deeper and deeper and you naturally relax. It will move lower and lower into your diaphram. It takes a lot of practice as our minds are very busy and hard to calm down.

I find that I enter this state where I am viewing my sub conscience mind. I bounce in and out of it. When I bounce out I bring my attention to my breathing again. It is like the state when you are just falling asleep but not yet asleep. If you think your conscience mind it busy you should see what is going on in your sub conscience mind. It is wild. If relaxed enough I can also purposefully stimulate tingly sensations up my spine and into my brain. I can also do the same thing in my prefrontal cortex and kind of enter this very happy place. The sub conscience mind is where intuition and revelation bubble up from.

I have been doing it on and off for about twenty years. I do it laying down alot and fall asleep. This is not recommended.

It is pretty much proven that whatever level of practice you are at it is highly benificial. There are other methods too besides the way I do it. Using a Mantra. Guided meditations.

You will find the more you do it the more you will notice throughout the day when you are getting stressed and your breathing starts rising in your chest. You will start to automatically notice it and calm your breathing down and relax and feel the stress fall away.

There are some free guided ones here at UCLA
Free Guided Meditations | UCLA Mindful Awareness Research Center

Meditation: Take a stress-reduction break wherever you are - Mayo Clinic