Help with Theme

I’m unsure on how to use this plugin with Rowling – WordPress.com theme.

I guess making changes to this part of style.css would have to do something with it. Not sure of anything.

/* -------------------------------------------------------------------------------- */
/* !## 14. Pagination */
/* -------------------------------------------------------------------------------- */
/* Page Title --------------------------------------- */

.page-title {
	border-bottom: 2px solid #ddd;
	position: relative;
	text-align: center;
	z-index: 1;
}

.page-title h4,
.page-title p {
	color: #666;
	font-size: 0.85rem;
	font-weight: 900;
	letter-spacing: 1px;
	line-height: 110%;
	text-transform: uppercase;
}

.page-title h4 {
	border-bottom: 2px solid #0093C2;
	float: left;
	margin-bottom: -2px;
	padding: 0 0 10px;
}

.page-title p {
	float: right
}

.page-title p .sep {
	color: #AAA;
	margin: 0 5px;
}

/* Posts Navigation --------------------------------------- */

.post-navigation {
	border-top: 2px solid #ddd;
	display: table;
	width: 100%;
}

.posts-navigation .nav-previous a:before {
	content: "\2190\00a0";
	font-family: 'FontAwesome';
}

.posts-navigation .nav-next a:after {
	content: "\00a0\2192";
	font-family: 'FontAwesome';
}

/* Archive Navigation --------------------------------------- */

.archive-nav {
	border-top: 2px solid #ddd;
	color: #777;
	margin-top: 60px;
	position: relative;
	text-align: center;
}

.archive-nav ul {
	text-align: center;
}

.archive-nav li {
	display: inline-block;
	margin-top: -2px;
}

.archive-nav a {
	border-top: 2px solid transparent;
	display: inline-block;
	color: #777;
	font-size: 0.85rem;
	font-weight: 900;
	letter-spacing: 1px;
	padding: 15px 10px 10px;
	text-transform: uppercase;
}

.archive-nav-older,
.archive-nav-newer {
	position: absolute;
	top: 0;
}

.archive-nav-newer {
	left: 0
}

.archive-nav-older {
	right: 0
}

.archive-nav-older a:after {
	content: "\00a0\2192";
	font-family: 'FontAwesome';
}

.archive-nav-newer a:before {
	content: "\2190\00a0";
	font-family: 'FontAwesome';
}

.archive-nav .active a {
	border-top-color: #444;
	color: #444;
}

.archive-nav a:hover {
	border-top-color: #0093C2;
	color: #0093C2;
}

.archive-nav li + li {
	margin-left: 10px
}

Would be thankful if I could get any help here.