The Facebook API doesn’t include whether or not a post is pinned, however you can achieve the same result by manually moving a post to the top of your feed using the following JavaScript snippet:

$('#cff .cff-item').first().before( $('#cff_your_post_id').addClass('cff-pinned') );

You’d need to replace the “cff_your_post_id” part in the snippet with the ID of the post you want to pin to the top of your feed. You can find the ID of the post you want to pin by right clicking on it and clicking “Inspect Element”. You should see an ID on the cff-item element as shown below.

Replace the ID in the snippet with that ID, and then add the code to the plugin’s Custom JavaScript section (Customize > Misc > Custom JavaScript).

To change the styling of the pinned post you can add CSS to the plugin’s Custom CSS section, for example:

.cff-pinned{
padding: 10px !important;
border: 1px solid rgba(0,0,0,0.3);
box-shadow: 0 0 10px 0 rgba(0,0,0,0.15);
}