How to create button nex/previous

code :

<?php next_post_link_plus( array(‘order_by’ => ‘post_title’,’in_same_cat’ => true, ‘ex_cats’ => ‘2’, ‘ex_cats_method’ => ‘strong’) ); ?>

css:

.btn {
background: #3498db;
background-image: -webkit-linear-gradient(top, #3498db, #2980b9);
background-image: -moz-linear-gradient(top, #3498db, #2980b9);
background-image: -ms-linear-gradient(top, #3498db, #2980b9);
background-image: -o-linear-gradient(top, #3498db, #2980b9);
background-image: linear-gradient(to bottom, #3498db, #2980b9);
-webkit-border-radius: 28;
-moz-border-radius: 28;
border-radius: 28px;
font-family: Arial;
color: #ffffff;
font-size: 20px;
padding: 10px 20px 10px 20px;
text-decoration: none;
}

.btn:hover {
background: #3cb0fd;
background-image: -webkit-linear-gradient(top, #3cb0fd, #3498db);
background-image: -moz-linear-gradient(top, #3cb0fd, #3498db);
background-image: -ms-linear-gradient(top, #3cb0fd, #3498db);
background-image: -o-linear-gradient(top, #3cb0fd, #3498db);
background-image: linear-gradient(to bottom, #3cb0fd, #3498db);
text-decoration: none;
}

help me!
thank