QGIS plugin docs: add reference to testmodels

docs/qgis/index.qmd

@@ -39,7 +39,8 @@ Documentation on the Time Series widget can be found in the [iMOD documentation]
 
 ### Prepare your model
 
-Open example model `database.gpkg` or create a new model.
+Open an existing model or create a new model.
+As an example of an existing model, you can use the "basic" model from `generated_testmodels.zip`, see the [download section](../index.qmd#sec-download).
 
 ![](https://user-images.githubusercontent.com/4471859/224939126-b38f0eed-2e89-4120-b541-5b8c31798c09.png){fig-align="left"}