How to setup 1. showcase page and 2. facebook like button in the sharethis field

Hello Kate ! 
– To create a showcase page as our demo, you can do as the following: 
1. After creating a Showcase posts (select categories is: Showcase)
2. Move through Menu > Select the Showcase in the  Categories arena, click the Add to menu button.
Notice: If you still face the issue, please send me username & password of your site (via private answer) for further checking.
–  To use only facebook like button on that filed, you can add the following code to the Header Code:

 <style>
.st_plusone_button, .st_email, .st_twitter, .st_sharethis {
    display: none;
}
</style>

Hope this helps !