First byte time and leveraging browser caching?

I’m using webpagetest.org. I’ve got a pretty good score going on, but it’s telling me I need to leverage the following links for caching. What can I do to fix this? Also, my first byte time is an F. How do I get that up???

This is my web test report http://www.webpagetest.org/performance_optimization.php?test=131124_X3_D2G&run=1&cached=0.