To run HTTP/2 you just need to upgrade to Nginx 1.9.5 or later
Assuming your nginx is already configured with ssl
Change
listen 443 ssl;
to
listen 443 ssl http2;
and reload your config:
$ service nginx reload
https://blog.cloudflare.com/tools-for-debugging-testing-and-using-http-2/
https://www.bjornjohansen.no/enable-http2-on-nginx