You can add custom code to your site using the Squarespace Code Injection
First, copy the embed code from Reboo
In Reebo click on your Project to open it
At the top right, click the "Connect Reboo to your website" button
Click Copy to copy the embed code
Paste Embed Code to Squarespace
In the Home Menu, click Settings
Click Advanced
Then click Code Injection.
Paste the code into the Header box and click Save