How to save and download diagrams
In the top panel, click on the "Download Image" button.
You will then be presented with a dialog with 3 image format options:
Select one of the options (Pick "JPG" if you are unsure. Learn more about image formats and how to decide which to pick).
After downloading, you can insert this image in a document, presentation or otherwise share it.
If you need to edit the diagram in the future, consider also saving your diagram to the Cloud. See the below Related article.