First I make a dark black background, and place a Earth images in the middle of it.
After that, I use sponge tool to remove the color of the right side of the the earth which telling us that is a dark side of earth.
And then I drop a trash images in the dark side of the earth which mean half of earth are filled by trash.
Then I put the tittle, persuasive text and explanation on the poster to tell what our message.
At last, I leave my group logo to inform people that we the maker of this poster.