[Plugin: Portfolio Slideshow] Thumbnails not on top/not centered

I love the gallery so far–but I’m having a few issues. I’m not a programmer or very knowledgeable in coding, so I’m trying to figure it out as I go. At this point, I know the images need to be resized, I’m just trying to get placeholders in the meantime. Here are the three problems I have.

Here’s my website so far http://www.christinaforshay.com

1. thumbnails won’t change size. I’m changing them under Settings>Media, but no changes take effect

2. thumbnails won’t move to top of image. I really have no idea how to do this.

3. Thumbnails aren’t centering to the main image.

Any help you could offer would be awesome!!!

Thank you