Horizontal Widgets on Same Line

My site is http://www.dinoberry.com/blog
If you need specific code, let me know and I’ll post it. I’m unsure what code I need to be editing.

I want to have widgets side by side. I’ve checked multiple sites and solutions haven’t been particularly useful. This seems like something that should be very simple to do.

The template is just a general template that I selected because I like it the best. I’m slowly editing things with the goal of achieving a distinct template (not even close yet).

If someone has a suggestion for a plugin, I don’t mind that. However, I’m also trying to improve my coding abilities and I’ll want to find a solution anyway.

An aside: Is there a way to center the border-top (the white line at the bottom)? I temporarily cheated by just increasing the width but I’m curious how one might achieve, say, a centered line above text.