Customer.io Integration Guide
If you will not be apart of the Union workspace for Customer.io, learn how to get this setup in your Union org!
To start, go to your Settings -> Customer.io page in Union. It should look like this:

Click the Setup button. Make sure to click the 'Enable Customer.io' toggle at top.

We'll get the information for the next three fields in the steps below.
Now, sign up or login to your Customer.io account at fly.customer.io. You should see a screen like this:

Click the icon in the bottom-left of the screen (Integrations). Then, click Customer.io in the next screen:

You'll want to copy the Site ID and Api Key values (there should be a handle clipboard icon to the right that will copy the value of each to your clipboard when you mouseover each field. Then, copy it to the Union Customer.io config screen:

You'll also need to generate an App Key, which you can do by clicking on 'Create App API Key':

Make sure it's selected the correct workspace, click 'Create App API Key' again:

Now copy this link to the App API Key field in the Union settings:

Voilà! You should be good to go.
Contact Union Support should you have any questions or if you need historical data published.