esmi on "How do change archives page on Twenty Fourteen theme to a 2 column grid?"

I'm sorry but it is really beyond the scope of these forums to deal with general CSS issues. Try a dedicated CSS resource such as http://www.css-discuss.org/ instead. In the meantime, try using Firefox with the Firebug add-on for this kind of CSS work. Or use whatever developer tool is available in your web browser.
http://getfirebug.com/