How can I take just a part of CSS from other site's when using bootstrap?

I have the website using bootstrap for its css style.
What if I want to take just a little bit of part of css from other website?
What would be the best way? I tried to use one of the function 'inspection' with Firefox.
It shows all the hierarchy and its styles stated for each class.

The thing I really care about is confliction between bootstrap and the new css.
How would you guys solve this if you want to take just a little bit part of other css?

Solution

First of all don't pick up styles from other's website before a prior permission from the site administrator...

For the bootstrap..I've never used it but still according to me you can over-ride the default bootstrap styles by using CSS !important

I tried to use one of the function 'inspection' with Firefox. It shows all the hierarchy and its styles stated for each class.

Styling a single element is never dependent on a single class, it inherits some of the properties from the parent class too...For example

<style>
.wrapper {
   color: #ff0000;
}

.hello {
   background-color: #aaaaaa;
   / *Width and color of the parent div is inherited */
}
</style>

<div class="wrapper">
   <div class="hello">Hello World</div> <!-- So actually this uses color and width of .wrapper and background-color of .hello -->
</div>