By default, puppet only submits a hiera query when it is trying to find a value for a class parameter. OUtside of that, hiera doesn’t get used by puppet. As for your manifests, you will mainly be using data available from facter and puppet built-in variables.
However if there is certain data that you want to use in your manifests, but are stored in yaml files. Then you can instruct puppet to perform a hiera lookup using a number of functions: