How to modify the margin and padding when using Bootstrap?

Question

I'm using Bootsrap, and it seems like Bootstrap is adding to much margin and padding. I've tried this 2 lines eachtime but with no luck.

.margin-0{
   margin: 0;
}

<div class="col-md-2 margin-0">
</div>

That didn't resolve the problem. I've then tried this

.col-md-2{
  margin: 0;
}

Nothing happened either, still have all those margin and padding that I'd like to reduce.

How do I reduce margin and padding to make this

look like this.