Dymo is one of the most popular brands of label makers, used in many kinds of offices. Once the D1 label maker runs out of labels, a new cassette needs to be inserted.
Open the label maker.
Pull the old cassette from the label maker.
Insert the new cassette. Make sure the labels on the cassette are facing outward. The label maker has an arrow drawn on the inside showing you how to face the cassette.
Print a test label to make sure the cassette is positioned properly inside and facing the correct direction.