After you've opened your canvas click on sharing icon at the bottom on the menu on your right hand
Then you can do this by simply sharing a link of your project to your team.
You can share by People (For members already part of the Fronter team) , Email or by sending a link.
Inviting them by adding their email as you do in Google Docs.
Or just select them if there are already part of your team
People don’t even need to make an account to leave comments when they are invited by a link & they can comment as guests. This is perfect to collaborate with clients. Your clients don’t need to install anything or sign up for an account. They can just click and type to leave a comment anywhere.