You can specify who the hiring team are within an interview stage. They will need to be setup as a user of Pinpoint in order for you to add them. They will also need to be assigned permissions to view the job (see How to Add/Edit/Remove a Team Member's Permissions).
Additionally, in order for interviews to synchronise with their calendars they will need to have setup the calendar synchronisation integration.
First, browse to the navigation on the left hand side of your Pinpoint Admin Screen and select 'Manage Jobs' under the 'Jobs' section:
Click 'Manage Interviews' from the menu shown below:
If a Custom Hiring Workflow is applied to the job, you'll see a dropdown showing the various interview stages. Click the interview stage you want to edit:
Select which team members you want to add as members of the 'Hiring Team' from the dropdown as shown below:
Once you've finished adding your Hiring Team, click 'Update' on the right.
Now, any interviews that are scheduled will be synchronised with the hiring team's calendars.