In order to connect a MongoDB data source, head to the new data source page, and select MongoDB in the connection type dropdown.

Add your MongoDB connection string (read more on how to get your connection string here) and click Connect Database. This will test the connection to your database and add it as a data source you can use in your monitors.

For MongoDB queries, you will have to provide a filter query with a special keyword collection which corresponds to the collection you are querying. You can find more information on how to generate the filter query JSON data here.