Update dbt.md

Author: kurt-lu

src/segment-app/extensions/dbt.md

@@ -48,7 +48,7 @@ To set up dbt Cloud:
 
 1. In your Segment workspace, navigate to **Settings > Extensions**.
 2. Click **Manage dbt Cloud**.
-3. Add your dbt Cloud API key, and, optionally, a custom subdomain. Click **Save**.
+3. Add your dbt Cloud API key (this should be your dbt Personal Access Token ), and, optionally, a custom subdomain (by default, the subdomain is set to 'cloud'.  Your custom subdomain can be found in the url, for example https://cloud.getdbt.com/). Click **Save**.
 
 ### Model syncs
 
@@ -65,4 +65,4 @@ After you've successfully set up dbt with a warehouse and connected to your Git
 5. Click **Next**.
 6. Enter your **Model Name**, then click **Create Model**.
 
-To change a connected model, ensure that you've removed it from all active Reverse ETL syncs.
+To change a connected model, ensure that you've removed it from all active Reverse ETL syncs.