When you launch the See app you will be presented with an Invite friends button which will generate a link that you can share with your friends on whatever platform you like.
You can send the link by email, SMS, Slack, Messenger, WhatsApp, Facebook, or any other way to your friends.
The See link is special and works differently on Android, iOS or Web. The link starts with https://getsee.page.link/ and then a code. When the link is tapped on an iPhone or Android it checks if you have the app installed. If not, then you are taken to the app store where you can download the app. If you did have the app installed or just downloaded it then you will be taken to start the call with your friends. You may have to accept Microphone and Camera permissions.
On a desktop the same link will take you to the https://getsee.co web site where you can join a call.