Grouping categories

Hello,

I have 5 categories in my blog and divided them into two groups. So there are 3 categories under the first group and the rest two cats under the second group. It was done easily using the hierarchy of the categories. Let’s say as following.

US Cities – NYC
– DC
– LA

EU Cities – Paris
– London

Now I want to arrange the two groups in separated panes in my blog. Refering the example above, I would like to place the first group (US Cities) on the left side of my website while the second one (EU Cities) sits on the right pane.

Please teach me how to enable the “severance.” Since I am a newbie to the wordpress, detailed explanation would be highly appreciated.

Thank you.