Smart Optin is quite advanced to set up, as at first, you will have to create an “app” in both Google and Facebook (usually those are done using your business page name)… and needs previous experience with both Facebook and Google API…
For example in Google, once you land on that page you can create a new “Project” or use an existing one if you already use Google API for something else, once created just take the Client ID given by Google.
In Facebook, the term they use is “Apps” instead of projects, you’ll have to create an app using the link given to you on the Smart Optin panel, and then get the Client ID given by Facebook.
That part is not documented by us, as it really changes how both Facebook and Google handle Client IDs creation…