How do I sync my google calendar from my mac devices with IS

If I am out and about and add an appointment on my phone, is there a way that I can sync to my IS through Google Cal?

I do use iCal but find that Google synchronises with most things and use this as my core calendar, which then shows on all of my mac devices.

I don’t mind if this only works one way, but need it to be from Google Cal to IS.

Any help would be appreciated. I tried Chat and they directed me to this community.