How to add max-age for cache-control in request header?

I’m trying to enable caching for the website. I ran the website through Google PageSpeed Insights and it came back with this.

Leverage browser caching

Setting an expiry date or a maximum age in the HTTP headers for static resources instructs the browser to load previously downloaded resources from local disk rather than over the network.

I checked my request headers and it shows the cache-control as max-age=0, how can I change this so that I can leverage browser caching properly? Does any of the WPMU plugins fix this? Just to let you know, I also connected my Hummingbird plugin to Cloudflare as suggested by WPMUDev.