Hello @PoetSnow  You are on correct path. Creating the segment in Klaviyo would be the right way.

Hey  @PoetSnow 

So adding a tag is one way of doing it then building the segments afterwards, but my recommendation is:

1.  Create a new List in Klaviyo where you want these customers to end up.
2. In Zapier Select Klaviyo as the App
3. Create or Update Profile
4. In configure settings, you want to select the list you created as the destination 
5. the populate the data you have available from the webhook/source to the relevant fields
6. At the bottom of the configuration you can also add custom properties, such as the source, so you can build additional segments later if required.

Hope that helps!