To add or delete files, you can say ‘My Files’ and navigate to either ‘My Photos’‘My Media’ or ‘My Documents’. From there, say ‘Edit Mode’ to switch to the edit mode. Say ‘Select Item #’ to select items. Once selected, you can say ‘Delete Selected’ to remove from the HMT-1 or HMT-1Z1. To add files to your HMT-1 or HMT-1Z1, you must connect your device to PC or Mac using the Micro USB adapter and USB-C cable (Included). Note that the Micro USB adapter must be used for all data transfer, as the USB port is Power Only. 

If using a PC, a disk icon will appear representing HMT-1/HMT-1Z1. You can navigate the files and folders of HMT-1/HMT-1Z1 by clicking on the HMT-1/HMT-1Z1 icon. Drag files onto HMT-1/HMT-1Z1 to add them, and drag files from HMT-1/HMT-1Z1 to the trash can to delete them. If you are connecting to a Mac, you will need to download and run the Android File Transfer application, available here: 
Functionality is the same as above for Mac once Android File Transfer is installed.