You unzipped the folder and JUST moved the theme itself, correct? Don’t move the entire zipped folder to wp_content -> themes, just the folder with the theme name that’s inside the zipped folder.
Do you mean you want it to be fixed on the bottom regardless of what size the window is?
So you downloaded the theme and dragged it into wp_content > themes folder, right?
After that, go to the Themes section of the Dashboard (under Appearance) and select “Activate” on one you want to use (if you have dragged it into the proper folder, it should appear below the theme that’s currently being used).
Go here:
https://developers.facebook.com/docs/reference/plugins/like/
…and follow the directions. You’ll have to verify your account via text (to prove you’re not a spambot).
Copy and paste the second set of code (the one that starts with <div> vs. <iframe>) into the footer.php document just before the closing </footer> tag (or wherever you want to insert it).