Sharing Calendars

Hello -

I am trying to use the "Shared Calendars" feature. I have read all the documentation which says that I can just click on the "Calendar" icon and then click on the "Share Calendar" icon. However, the "Shared Calendar" icon does not appear. I am currently using a trial version - Microsoft Office 365 Plan p1. Does this have ALL the functionality of the purchased version? Why am I not able to share a calendar with other users I have set up?

Thank you,

Neil.