It's really simple to automatically add Zoom web conferencing to meetings scheduled with FreeBusy. You just have to connect it once and you're done. Then, it's just up to you if you want to select Zoom as your conference call venue.
3). Click on Integrations tab and Link Another Integration.
4). Scroll down the list to find Zoom and click Add.
5). Sign in with your Zoom credentials and your Zoom account will be automatically linked to your FreeBusy account.
Then refer to this guide on how to select your default conferencing provider for meetings scheduled with FreeBusy.