Sometimes you may want to create alerts to notify your team when data changes in unexpected ways. We believe alerts should be simple and easy to understand. Thus we've restricted alerts only to single line visualizaitons.
Effectively you want to boil down what you want to alert on to a single line. That might be user sign ups. It might be number of errors, etc.
To create an alert, go to the visualization tool, click on the single line visualization and then click Export -> As Alert