Http2 Server Push support

Quick question/clarification on using Server Push with Http2.

So, I installed libnghttp2, then compiled Apache 2.4.18 from source with http2 support and created some self signed certs to use https.

I then added in directive Protocols h2c http/1.1 and created a vhost including:

<Location /index.html>
    Header add Link "</css/site.css>;rel=preload"
</Location>

so I can test Server Push. Hitting my front end with Firefox I get the h2 header returned as well as a Link Header that's value is /css/site.css but my css isnt preloaded.. Not sure if I am fundamentally misunderstanding what Server Push is doing or not doing or whether I have done something wrong.

I've tried with a few variations of the css value and location value but with no success. Been googling for a while, but to no avail, so any point in the right direction would be great.