for an ebike biz: Northwind without existing customers etc

[stan.heard]

Hi, I'm a newbie to Access and have just started a an eBike business. Northwind seems to have all the data relationships I will need for the next while.However I can't seem to be able to delete the records from the infinity boxes on the right of the relationship pane as its suggested. Could someone walk me through deleting these specific customers, suppliers ect records so I can just have my own customers and suppliers?