where do I change css on products

Hi

This is just a really little thing - purely aesthetics!

I want to change the way the categories are displayed on products as they are quite ugly and there is no space between the buy button and the categories. I have a screen shot of what I want to change.

Being a novice at Wordpress I just want to make sure I don't break anything by changing the wrong file or changing the wrong thing.

I hope you can help with this.

Robyn