“It is our duty to concentrate all our influence to make popular that which is sound and good, and unpopular that which is sound” (not good)

~ Joseph Smith

What i think he is trying to say is that it is up to us to make a notice of what’s right and sound good and to not make a trend of what is bad. To concentrate on what’s positive in your life such as respect, honesty, and a good name. These are things that sound good.  It’s better to make a trend of what’s right then something that is wrong so we can influence the younger generation so they can make better choices. He wants us to make popular on what’s good because he wants everybody to know what is the right thing. Something you can do to promote to make popular is to help those in need.