To delete a specific database in the cluster:
Go to the Database section and click on the cluster.
Go to the Databases tab.
Click on the three dots next to the database.
Click Delete.
Confirm the action.
To delete the whole cluster, with all databases and database users within it:
Go to the Database section.
Click on the three dots and click Delete database.
Confirm the action.
Or:
Go to the Database section and click on the cluster.
Go to the Configuration tab.
Click Delete database.
Confirm the action.