1. start php-fpm
2. point yaws to the ip:port of the php-fpm process (you cant use sockets, so you need to change config of php-fpm to listen on port)
3. maybe whine because you cant use .htaccess files
As most php apps today are based of single index.php files, you maybe want to use something like my error_mod, which redirects not found paths first to the php script:
actually I missused things a bit, as I did use the first solution I got working.
Also you need to care about securing directories for older applications.
The sure way to tell how php is running is via the phpinfo()
coming from apache you first need to learn, that php-fpm runs as a complete independent process from the webserver and has its own worker management.
Hope it helps, if you have more specific questions, just continue writing to the list.