This article explains how to change all post links into design like this:

You can use CSS code below: 

.post-content a:after {
font-family: FontAwesome;
content: "\f08e";
display: inline-block;
padding: 0 3px;
vertical-align: middle;
}

.post-content a:hover {
color:#29aae3!important;
}

In this article you can find information how to add custom CSS to any WordPress Theme:

How to add CSS code that is future update compatible