Slider aligned to left, how to centre?

Hello,

I’m trying to alter both the thumbnail size and alignement of the slider option. What I have is this: https://kkat.mavenpromedia.com/business-cards/

What I want is this: https://i.imgur.com/B71nFfP.jpeg

Can anybody help me out?

Thanks.

The page I need help with: [log in to see the link]