Calendar Plugin – How to make it so “authors” can add events

I have installed Paranoid’s calendar plugin:

https://n0id.hexium.net/

And have got it working nicely, however the only place to add events is in Options > Calendar which is only available to administrators.

However I need to make this available to Authors too as I am using the calendar as a training room booking tool and don’t want to have to manage the room calendar all for myself.