CSS Form Help

Hey All! I’m a novice and am having some issues with my form at https://youpet-cha.com/reg/

I wanted to work on some CSS to make it match some of my other forms on my site. But I can’t seem to locate the correct CSS file that I should modify or how to do that. I was able to modify my search form, but this one isn’t working for me.

Anyone have any clue? Thanks for the time!

– Joe

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