Find a quiet space or room. I like to take my shoes off and sit cross legged, but really you should sit in a way that is most comfortable.
Set your timer for 8 minutes, and use a notification sound that is least jarring. (I use the free "timer" app which has a soft bell called "meditation") Close your eyes and start your timer.
Clear your mind and focus on your breathing. As you breathe in, say the word "in". Breathing out, say the word "out." You can try variations of words, but the goal here is to focus on something.
Heres the hard part: everything possible will pop into your mind. Your job, your wife, your kids, pretty much everything will try to take a priority over the nothing you are trying to accomplish.
Your job is to peacefully acknowledge the thought and let it go, returning back to your breathing. It's as if you are fishing; you catch a thought, look at it, and let it go.
This is the hardest part about meditating (and life): managing the distractions. It's easy to get down on yourself, think you're not good at it and give up. When you think this way, just let it go!
When your time is up, take a deep breath and stretch. You have completed your first meditation! Each session adds up, and as you do more and more, it becomes easier to clear your mind.
After a few months of daily meditation, it will become easy to just turn off your negative, self-defeating thoughts. You will achieve greater clarity, and be able to better manage distractions. Peace!