Adding code for NGINX to change browser cache limit

I added Hummingbird Peformance Cache yesterday. After the initial setup, I received a message that four of my browser cache types don't meet the recommended expiry period of 1 year. Three are set at 1 day, and one is set at 7 days. I have listed them below.
jsJavaScript
1 day
cssCSS
1 day
mediaMedia
7 days
imgImages

Hummingbird detected that my servver is NGINX. I called BlueHost, and an agent confirmed that. Because I didn’t know how to access the NGINX file, I asked the BlueHost agent for help because Hummingbird said to contact my hosting provider. I read the location that Hummingbird said where the files are located. The agent said he couldn’t do that for me. A second BlueHost agent said the same thing. So that’s why I am contacting you for help.

Thanks for helping me.

The page I need help with: [log in to see the link]