You have at least two active widgets of the plugin. So, please, follow these steps:
1) Make a backup of your current CSS styles (just in case…). Take note that you have multiple places where you have entered styles for Posts in Sidebar, so search for them.
2) Remove every CSS style for Posts in Sidebar, for example:
#pis_posts_in_sidebar-2 .pis-title { font-size: 18px !important; }
and multiple others. You have styles either in the widget admin and in WP Custom CSS plugin.
3) Paste this styles in a Posts in Sidebar widget or in your current theme’s styles.css file or in WP Custom CSS plugin:
#pis_posts_in_sidebar-2 ul.pis-ul,
#pis_posts_in_sidebar-3 ul.pis-ul {
margin-top: 1em;
margin-left: 1em;
line-height: 1.2;
list-style: none;
}
#pis_posts_in_sidebar-2 li,
#pis_posts_in_sidebar-3 li {
margin-bottom: 10px;
overflow: hidden;
width: 315px;
height: 105px;
position: relative;
}
#pis_posts_in_sidebar-2 .pis-thumbnail,
#pis_posts_in_sidebar-3 .pis-thumbnail {
margin-bottom: 0;
height: auto;
height: 105px;
overflow: hidden;
width: 150px;
position: absolute;
}
#pis_posts_in_sidebar-2 p img.pis-thumbnail-img.alignleft.wp-post-image,
#pis_posts_in_sidebar-3 p img.pis-thumbnail-img.alignleft.wp-post-image {
margin-bottom: 0;
margin-top: 0px;
max-width: 100%;
height: auto;
display: block;
}
#pis_posts_in_sidebar-2 > ul > li > p.pis-title,
#pis_posts_in_sidebar-3 > ul > li > p.pis-title {
padding-top: 0px;
padding-bottom: 0px;
margin-bottom: 0px;
position: absolute;
width: 157px;
height: 105px;
display: table;
left: 157px;
}
#pis_posts_in_sidebar-2 a.pis-title-link,
#pis_posts_in_sidebar-3 a.pis-title-link {
display: table-cell;
vertical-align: middle;
}
These styles, among other aspects, will center the text and the image.
Let me know, please.