Digital Stamps and Cutting Files can be normally downloaded from the "My Account" page, directly after placing your order. 

Simply click the link(s) to open in your browser or PDF reader and select a safe location on your computer to save the PDF file(s). In the case of Cutting Files, the download will be in the form of a Zip file containing the image in various formats. 
Because there is a limit to the timescale and to the number of times an item can be downloaded, please ensure you save each of them to a safe location on your computer at the time of, or soon after, downloading them.

In the same way that you would look after a physical stamp or other items, you should take responsibility for the safe storage of your digital assets. This would include keeping a copy on whatever backup facility you employ, whether an external backup drive or a cloud storage solution such as Dropbox, Microsoft Cloud or Google Drive. (Each of these offers a generous amount of free storage space.
I do hope this helps. Please raise a support ticket if you require any more assistance.