Hi blaster,
Based on your description and the tags, it seems that you are using the pre-upgrade Office 365 (Am I using Office 365 after the service upgrade?) and the Office 365 Plan P1 now. If I’m incorrect, please feel free to correct me. Otherwise, please continue reading the following information.
For your first question” Does the Microsoft Office 365 plan P1 include Office for Mac?”:
Office 365 Small Business (Plan P1) doesn’t include Office desktop applications. So, you need to purchase the Office 365 ProPlus subscription additionally.
For your next question “how/where do we get and use it?” :
You need to log in to Office 365 with an administrator account and click on Purchase on the admin page, and then purchase the Office 365 ProPlus licenses.
If you have any questions, please feel free to let me know.
Thanks,
Kevin Huang