You need to add a new data source before creating dashboards.
Notice: Only users in Global Team can add data source
On the left menu panel, click Configuration -> Data Sources -> Add Data Source
Choose prometheus if you already have one deployed, use Static Data otherwise. The Static Data contains some demo data for testing pupose.
Enter an appropriate name for you data source, we will use 'test' in this tutorial. You can set the data source as default if desired, this saves you from explicitly specify data source for every dashboard. There can only be 1 default data source at a time.
Enter the server address HTTP -> URL if using prometheus data source
Click Save&Test, you should see a Succeed notification. If you get an error saying get xxx, dial tcp, connect refused, check the prometheus address
View existing data source
On the left menu panel, click Configuration -> Data Source