Log in to your Intercom account and go to user settings page by clicking user icon on the bottom left.
Go to Developer Hub page by clicking "Developer Hub" under "Developers" menu.
If you don't have an app for the workspace create one.
Click the app for your target workspace and go to "Authentication" tab under "Configure" and you can see an access token there.
Enter the access token and click Add button.
Repeat this process for all Intercom accounts you would like to connect.