First thing you'll need the overwatch game on ps4 or Xbox one. Make sure your parents are ok with the game it is t for teen so some parents might not like it. If your not allowed sorry.
I chose my ps4. But you can you use what ever you have. I just prefer ps4. Nothing against you.
Then load it up and go into quick play and choose your character. I chose Genji but pick whoever you like. Just keep in mind that I have played this game ALOT so I'm doing first try so you might have
When you are in the game there will be a little circle at the bottom of the screen. Wait for it to hit 100 percent.
When you hit 100 percent it will look like this. (You will have to eliminate the other team players)
After you have 100 percent find the enemy and press triangle for ps4 and Y for Xbox one. You will achieve your goal when you see this on your screen.
You will need lots of practice to achieve there are really good players and it may be difficult at first but practice makes perfect. So have fun practice and be awesome!