D-Link DNS-320L User Manual page 243

Section 4 - Configuration
In the Add to Zip window, select the zipped file you want to have the file added
to. Click the checkbox and click Apply.
The wizard will add the new file to the zipped file. Your existing Zip file will have
increased in size due to the addition of the new file(s).
D-Link ShareCenter DNS-320L User Manual 237